International Journal of Psychophysiology, I (1989) 35-45 Elsevier 35 PSP 00219 The contingent negative variation in a Go/No Go avoidance task: relationships with personality and subjective state Diana Brown’, Peter Fenwick 2 and Rick Howard 3 ’ British Airways, London (U.K.), ’ Institute of Psychiatry, London (U.K.) and -’ University of Otago, Dunedin (New Zealand) (Accepted 31 May 1988) Key words: Contingent negative variation; Impulsiveness; Cognitive function; Laterality; Stress; Activation: Arousal; Anxiety Howard et al. (1982) reported an association in mentally abnormal offenders between psychometric impulsiveness and the degree of differentiation in the contingent negative variation (CNV) recorded at the vertex between Go and No Go conditions in a Go/No Go signalled avoidance task. The present study aimed to investigate whether this finding extended to two samples of young, hual%y< volunteers using a variety of impulsiveness-related measures. As well as examining the Go/No Go CNV recorded from the vertex. the present study investigated the Go/No Go CNV recorded bilaterally at central (C3 and C4: Experiment 1) and temporal (T3 and T4: Experiment 2) electrode derivations. The study also investigated relationships between the Go/No Go CNV and subjective state, including stress and arousal as measured by a mood-adjective checklist, as well as several task-related state measures. The Go CNV recorded at the vertex was found to relate to a variety of impulsiveness-related measures, in particular to Eysenck’s Impulsivity. Venturesomeness and Psychoticism. The Go/No Go CNV recorded at temporal sites was more closely related to measures of Emotionality. While the Go CNV appears to be an electrocortical index of a neuropsychological system mediating subjective stress, the No Go CNV appears to index subjective arousal. Results are interpreted in terms of orthogonal ‘primary’ and ‘secondary’ appraisal processes (Folkman et al., 1979), and their implications for Gray’s (1982) neuropsychological theory of anxiety and Tucker and Williamson’s (1984) neural control systems model of human self-regulation are outlined. INTRODUCTION Previous studies of the Contingent Negative Variation (CNV) in mentally abnormal offender samples by Howard et al. (1982) using a Go/No Go avoidance paradigm, have indicated that the amplitude of the Go CNV recorded from the vertex, and the degree of electrocortical differenti- ation between Go and No Go conditions, are inversely related to a psychometric measure of impulsiveness, Blackburn’s Impulsivity (Im: Blackburn, 1971). Highly impulsive patients showed low Go CNV amplitude and poor electro- Correspondence: R. Howard, Department of Psychological Medicine, University of Otago Medical School, Box 913, Dunedin, Otago, New Zealand. cortical differentiation. The present study ex- amined whether this finding of an inverse relation- ship between impulsivity and electrocortical dif- ferentiation in the Go/No Go task extended to samples of normal, healthy volunteers. An aspect of the Go/No Go CNV not previously investi- gated by our group is its topographical distribu- tion and its possible lateralization, and the possi- ble relationship of these to personality and subjec- tive state variables. This aspect was also explored in the present study. It is increasingly recognized that impulsivity is not a unitary trait. For example, Eysenck and Eysenck (1977) distinguish between 4 sub-traits of impulsivity: risk-taking, non-planning, liveliness’ and narrow impulsivity. Similarly, Barratt (1985) distinguishes between 3 sub-traits of impulsivity derived through factor analysis: cognitive, motor 0167-8760/89/$03.50 0 1989 Elsevier Science Publishers B.V. (Biomedical Division)
Transcript
International Journal of Psychophysiology, I (1989) 35-45
Elsevier
35
PSP 00219
The contingent negative variation in a Go/No Go avoidance task: relationships with personality and subjective state
Diana Brown’, Peter Fenwick 2 and Rick Howard 3 ’ British Airways, London (U.K.), ’ Institute of Psychiatry, London (U.K.) and -’ University of Otago, Dunedin (New Zealand)
Howard et al. (1982) reported an association in mentally abnormal offenders between psychometric impulsiveness and the degree
of differentiation in the contingent negative variation (CNV) recorded at the vertex between Go and No Go conditions in a Go/No
Go signalled avoidance task. The present study aimed to investigate whether this finding extended to two samples of young, hual%y<
volunteers using a variety of impulsiveness-related measures. As well as examining the Go/No Go CNV recorded from the vertex.
the present study investigated the Go/No Go CNV recorded bilaterally at central (C3 and C4: Experiment 1) and temporal (T3 and
T4: Experiment 2) electrode derivations. The study also investigated relationships between the Go/No Go CNV and subjective state,
including stress and arousal as measured by a mood-adjective checklist, as well as several task-related state measures. The Go CNV
recorded at the vertex was found to relate to a variety of impulsiveness-related measures, in particular to Eysenck’s Impulsivity.
Venturesomeness and Psychoticism. The Go/No Go CNV recorded at temporal sites was more closely related to measures of
Emotionality. While the Go CNV appears to be an electrocortical index of a neuropsychological system mediating subjective stress,
the No Go CNV appears to index subjective arousal. Results are interpreted in terms of orthogonal ‘primary’ and ‘secondary’
appraisal processes (Folkman et al., 1979), and their implications for Gray’s (1982) neuropsychological theory of anxiety and Tucker and Williamson’s (1984) neural control systems model of human self-regulation are outlined.
INTRODUCTION
Previous studies of the Contingent Negative Variation (CNV) in mentally abnormal offender samples by Howard et al. (1982) using a Go/No Go avoidance paradigm, have indicated that the amplitude of the Go CNV recorded from the vertex, and the degree of electrocortical differenti- ation between Go and No Go conditions, are inversely related to a psychometric measure of impulsiveness, Blackburn’s Impulsivity (Im: Blackburn, 1971). Highly impulsive patients showed low Go CNV amplitude and poor electro-
Correspondence: R. Howard, Department of Psychological Medicine, University of Otago Medical School, Box 913,
Dunedin, Otago, New Zealand.
cortical differentiation. The present study ex- amined whether this finding of an inverse relation- ship between impulsivity and electrocortical dif- ferentiation in the Go/No Go task extended to samples of normal, healthy volunteers. An aspect of the Go/No Go CNV not previously investi- gated by our group is its topographical distribu- tion and its possible lateralization, and the possi- ble relationship of these to personality and subjec- tive state variables. This aspect was also explored in the present study.
It is increasingly recognized that impulsivity is not a unitary trait. For example, Eysenck and Eysenck (1977) distinguish between 4 sub-traits of impulsivity: risk-taking, non-planning, liveliness’ and narrow impulsivity. Similarly, Barratt (1985) distinguishes between 3 sub-traits of impulsivity derived through factor analysis: cognitive, motor
and lack of planning. Blackburn’s Im correlates positively with measures of trait anxiety, hostility and aggression (Blackburn, 1980) and probably taps affective aspects of impulsiveness. This raises the question: of which of the impulsivity sub-traits is poor electrocortical differentiation a correlate? The present study therefore aimed to investigate in more detail the relationship between electro- cortical differentiation as measured in the Go/No Go paradigm and personality measures, including different measures of impulsivity and its sub-traits, as well as measures of social withdrawal and emo- tionality.
Another aim of the present study was to relate CNV differentiation and personality to measures of subjective state, in particular to measures of subjective stress and arousal using the Stress Arousal Checklist (SACL) (Mackay et al., 1978). Mackay et al. reported that in a factor analysis of mood items, stress and arousal emerged as inde- pendent factors. In another series of studies (How- ard et al., 1984) it has been found that a high degree of subjective stress (indexed by the SACL) induced by a ‘helplessness’ procedure was accom- panied by a temporary reduction in electrocortical differentiation between Go and No Go condi- tions. Using a similar Go/No Go paradigm to that adopted by Howard et al. (1980) and Howard et al. (1982), Glanzmann and Froehlich (1984) found that high trait anxious subjects showed poor Go/No Go differentiation in an ‘ego-threat’ condition relative to neutral and ‘pain-threat’ con- ditions, while low trait anxious subjects showed poor Go/No Go differentiation in the ‘pain- threat’ condition. Moreover, the degree of Go/No Go differentiation correlated with state anxiety in high, but not in low, trait anxious subjects.
Recently, Howard (1986) has speculated that Blackbum’s (1980) Impulsivity/ Psychopathy di- mension may correspond in state terms to a ‘cop- ing’ dimension, such that high Impulsivity/ Psychopathy corresponds to a high degree of in- ternal uncertainty and subjective stress arising from deficits in both ‘primary’ and ‘secondary’ appraisal processes (Folkman et al., 1979). Cogni- tive appraisal is a process through which the per- son evaluates whether a particular encounter with the environment is relevant to his or her well-being,
and if so, in what ways. In ‘primary’ appraisal, the person evaluates whether he or she has anything at stake in the encounter. In ‘secondary’ appraisal, the person evaluates what, if anything, can be done to overcome or prevent harm or improve the prospects for benefit (Folkman et al., 1986).
METHODS
Subjects Subjects were recruited through an advertise-
ment in a London weekly entertainment guide. They were all young right-handed males with no previous history of head injury, seizures, drug abuse or serious illness. They were drug-free and reported no visual or hearing problems. Subjects gave their informed consent and were paid for participation. Two samples of 12 subjects were selected for each of two experiments: Expt. 1 and Expt. 2. The mean age for the sample in Expt. 1 was 25.3 years, with a range from 20 to 36 years and a standard deviation of 5.4 years. The mean age for the sample in Expt. 2 was 25.3 years, with a range from 17 to 39 years and a standard deviation of 7.0 years.
Procedure On their arrival at 09.30 subjects were ques-
tioned about recent alcohol, caffeine, nicotine and other drug intake. Silver/ silver chloride electrodes were then attached to the scalp with collodion. Electrode placements were, for Expt. 1, Cz, C3 and C4; for Expt. 2, Cz, T3 and T4. In both experiments electrodes were also applied to a mid-frontal electrode and to the outer canthus of the left eye (for monitoring eye movements), and to a reference site on the tip of the nose. During electrode application, the subjects filled in 4 per- sonality inventories (see below). The tests were always administered in the same order. Subjects were then transferred to a comfortable chair in the experimental room for CNV recordings.
The Go/No Go recording session followed a previous session in which CNV was recorded using verbal and a spatial versions of a cognitive ‘match/mismatch’ task (Brown et al., 1988). The Go/No Go session started with 10 practice trials
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in which the subject was instructed to press a button held in the preferred hand as fast as possi- ble to an imperative tone (S2) which followed a warning tone (Sl). These 10 practice trials were used to determine a RT window for each subject’s Go/No Go session, this window being the average RT for the 10 practice trials. Following these practice trials, the Go/No Go CNV recording was commenced. This comprised a series of Go and No Go trials randomly interleaved. On Go trials, Sl signalled that a rapid response (within the subject’s RT window) was required to S2 to avoid a 3 s burst of 95 dB white noise. The duration of S2 was equivalent to that of the RT window, and onset of the white noise coincided with offset of the S2 unless a button press had occurred within the window, in which case S2 was terminated and the white noise omitted. On No Go trials, Sl signalled that the subject had to refrain from pressing to S2 to avoid the white noise, the occur- rence of which was contingent on the subject’s response (symmetrical Go/No Go paradigm). Button presses were made with the right thumb. Sl and S2 comprised 65 db SPL tones, either 1000 Hz or 2000 Hz counterbalanced for Go and No Go conditions across different subjects. Within each condition, both Sl and S2 tones were of same pitch. The duration of Sl was 0.25 s and S2 occurred 3.5 s after Sl onset. The inter-trial inter- val varied randomly between 5 and 15 s. Prior to the Go/No Go recording subjects were given a Stress-Arousal Checklist (SACL: see below) to complete, and were briefed as to the nature of the task to follow, care being taken to explain the difference between Go and No Go signals. It was explained that an aversive noise would follow a response either to a Go S2 that was ‘too slow’ or to a No Go S2. The criterion for being ‘in time’ was not made explicit to the subject. The subject was instructed to move his eyes as little as possible during the recording.
During the recording subjects were comfortably seated in an artificially illuminated test cubicle, facing a back projection screen with a central fixation point. The recording, which lasted 15-20 min on average, ended when 16 artifact-free Go and No Go sweeps had been accumulated to form the averages for ‘Go’ and ‘No Go’ conditions. The
subject was then given a further SACL to com- plete, as well as a task-related questionnaire (see below). Following this the subject was de-briefed and his electrodes were removed.
Acquisition and processing of EEG data EEG signals were recorded using an g-channel
SLE EEG machine from Cz, C3 and C4 (Expt. 1) and Cz, T3 and T4 (Expt. 2), all referred to a reference on the tip of the nose. Activity from Fpz referred to the outer canthus of the eye was re- corded as a check for eye movements. The time constant for the CNV signals was 10 s and, for the eye movement control channel, 1 s. HF filtering was 3 dB down at 70 Hz. The gain was set at 100 PV to give a 1 V output. The signals from the EEG machine were processed at a sampling rate of 64 Hz using the microcomputer-based Data Acquisi- tion in Neurophysiology (DAN) system (McAllis- ter et al., 1983). The hardware for this system operated in conjunction with software specially designed to control the data acquisition interface (for acquisition of CNV) and to generate the auditory stimuli used in the experiment. The 3 CNV channels, as well as the eye movement con- trol channel, were displayed on a TV monitor so that sweeps contaminated by eye movement artifact could be rejected visually on-line.
The CNVs (averages of 16 trials for each chan- nel and each condition) were stored. The DAN software, as well as giving a point by point plot, gave amplitude values at each of 12 consecutive points on the waveform, as well as the integral. Each of the 12 CNV amplitude values represented the mean of a 250 ms epoch relative to a 1 s pre-Sl baseline. The first epoch began 500 ms after Sl onset; the 12th terminated at S2 onset. An electrocortical differentiation measure was ob- tained by subtracting the No Go CNV integral from the Go CNV integral. A laterality index (Left-Right) was computed for each point on the waveform.
Psychometric measures of mood and personality (i) Personality questionnaires. The following
self-rated personality inventories were completed by each subject.
(1) Eysenck’s Personality Questionnaire (EPQ). This gives measures on scales of Extraversion (E),
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Psychoticism (P), Neuroticism (N) and on a Lie (L) scale. The EPQ E scale primarily taps the social (sociability) aspect of extraversion, rather than the behavioural (impulsivity) aspect (Rocklin and Revelle, 1981). The EPQ P scale aligns with Imp from the Eysenck Impulsiveness Scale (Eysenck et al., 1985: see below). The N scale is a general measure of emotionality. The L scale gives a measure of a tendency to give socially desirable responses.
(2) The Special Hospitals Assessment of Per- sonality and Socialization @HAPS), a lo-scale inventory devised by Blackburn (1979) to measure personality variables of emotional and social ad- justment of relevance to mentally abnormal of- fenders. These scales comprise the following: (i) L, Lie scale, a measure of a ‘socially desirable’ re- sponse tendency; (ii) Ex, Extraversion, a measure of both social and behavioural components of extraversion; (iii) A, Anxiety, a measure of the MMPI first factor, Emotionality; (iv) Pd, the MMPI ‘Psychopathic Deviate’ scale, measures lack of socialization; (v) I, Introversion, a measure of social withdrawal; (vi) D, Depression; (vii) T, Tension, another measure of the first MMPI fac- tor, Emotionality; (viii) Ag, aggression, measures acted-out aggressive tendencies; (ix) Im, Impulsiv- ity, a measure of lack of control over impulses; the behavioural component of extraversion; and (x) Ho, Hostility, a measure of covert suspicion and mistrust.
(3) Eysenck and Eysenck’s (1978) Impulsive- ness questionnaire (Is), a questionnaire which taps 3 separate aspects or sub-traits of impulsiveness, namely: Impulsivity (Imp), Venturesomeness (Vent) and Empathy (Emp). While Imp aligns with P from the EPQ (see above) and with Black- bum’s (1987) Belligerence measure (Barbour-Mc- Mullan et al., 1988), Vent aligns with social ex- traversion and Emp with neuroticism (Eysenck et al., 1985).
(4) Eysenck Personality Inventory (EPI). The EPI E scale breaks down into impulsivity (Im) and sociability (Sy) sub-scales. Scores on these sub- scales were obtained.
(ii) SACL measures. The SACL is a 30-item mood-adjective checklist for measuring changes in mood along two independent dimensions, ‘stress’
and ‘arousal’ (Mackay et al., 1978). ‘Arousal’ items reflect general level of alertness or activation, e.g. ‘ sleepy’, ‘ tired’, while ‘stress’ items reflect hedonic tone, e.g. ‘jittery’, ‘up-tight’.
(iii) Task related measures. These comprised a series of lo-point analogue scales on which the subject was asked to rate, from 1 to 10, the task difficulty, interest and stressfulness; his level of concentration on the task, and his alertness and tenseness during the task.
RESULTS
Go/No Go CNVs Go/No Go CNVs plotted across the 12 points
of the waveform are shown in Fig. 1 (for Expt. 1) and Fig. 2 (for Expt. 2). Individual CNV averages for 6 representative subjects from Expt. 1 are shown in Fig. 3. In Expt. 1 the Go CNV was of significantly greater amplitude than the No Go CNV at the vertex at all CNV points except the first (P < 0.05) and at other electrode placements (C3 and C4) over the last 5 points on the wave- form (P < 0.01). In Expt. 2 the difference in CNV amplitude between Go and No Go was again very highly significant at the vertex (P < 0.001 for the integral), and the difference was particularly marked over the last 3 points (P < 0.001). How- ever, the difference was much less marked at
lo’
PJ
5-
CNV POINTS
Fig. 1. Experiment 1: Go and No Go CNV values at 12 points on the waveform. Each point represents the average value over a 250 ms epoch. Circles represent values at the Cz recording site, squares values at the C3 site, and triangles values at the
C4 site.
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19
lo-
PV
5-
CNV POINTS
Fig. 2. Experiment 2: Go and No Go CNV values at 12 points
on the waveform. Each point represents the average value over
a 250 ms epoch.
temporal sites, being non-significant at T3 and T4 for the integral, and only significant at T4 for points 11 and 12 (P < 0.05). Moreover, the Go CNV amplitude was significantly smaller at tem-
Fig. 3. Individual averaged CNVs recorded in 6 representative subjects from Expt. 1. The upper two sets of traces show the
averaged activity for Go and No Go conditions in the eye
movement control channel; the lower two sets of traces show
the averaged activity at Cz for Go and No Go conditions.
poral sites than at the vertex (P < 0.05 for the integral at both T3 and T4).
Go/No Go CNVs and personality measures Relationships between Go/No Go CNVs and
personality measures were explored using the in- tegral of the whole CNV (CNV 11) as well as the integral of the last 3 points on the waveform CNV 12).
(i) Experiment 1. There were few significant correlations between CNV and SHAPS measures. A notable exception, however, was a significant negative correlation between scores on the Psycho- pathic Deviate (Pd) and amplitude of the Go CNV recorded at central sites, particularly at C3, where r = -0.75 for CNV 11 (P < 0.01); r =
-0.56 for CNV 12 (P < 0.05). The Go/No Go differentation measure correlated - 0.59 (P < 0.05) with Pd at both Cz and C3. In summary, subjects scoring higher on Pd showed a smaller Go CNV and poorer differentiation.
In addition, both A and Ag were inversely related to No Go CNV amplitude at both C3 and C4. Anxiety correlated negatively with No Go CNV 11 at C3 (r = - 0.62, P < 0.05) and at C4 (r - 0.65. P < 0.05), and with CNV 12 at C3 (r = -0.67, P < 0.05) and at C4 (r = -0.62, P < 0.05). Ag correlated negatively with No Go CNV 11 at C4 (r = -0.62, P < 0.05) and with No Go CNV 12 at C3 (r = - 0.53, P < 0.05) and at C4 (r =
-0.75, P -c 0.01). In summary, subjects scoring high on Anxiety and Aggression tended to show low amplitude No Go CNVs.
As may be seen from Table I, strong negative correlations were found between Go CNV ampli- tude and all measures of impulsiveness: Imp and Vent from Eysenck’s 1.5., the Impulsivity sub-scale from the EPI, and P from the EPQ. In addition, these measures correlated highly and significantly with the Go/No Go differentiation measure, but these significant correlations were entirely ac- counted for by correlations with the Go CNV; that is, more impulsive subjects tended to have low amplitude Go CNVs. No Go CNV amplitudes were not significantly correlated with these per- sonality measures.
(ii) Experiment 2. Relationships between per- sonality measures and CNV for Expt. 2 are shown
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TABLE I
Correlation coefficients computed between CNV measures (CNV II and CNV 12) and Eysenck personality rnetisures in Expt. 1
c3 CZ c4
GO No Go Go-NoGo Go No Go Go- No Go Go No Go Go-NoGo
CNVII
E -0.37
P - 0.45
N -0.02
L 0.02
Im - 0.48
SY -0.65 *
Imp -0.69 **
Vent -0.74 **
Emp - 0.48
CNVIZ
E - 0.39
P -0.62 *
N 0.14
L 0.01
Im -0.63 *
SY -0.63 *
Imp -0.77 **
Vent -0.63 **
Emp -0.47
- 0.57 -0.14 - 0.20
-0.09 - 0.48 - 0.59
-0.35 0.12 - 0.02
0.26 - 0.08 -0.12
0.03 - 0.49 -0.55 *
-0.18 -0.56 * -0.54 *
- 0.00 -0.67 * -0.75 **
0.15 -0.78 ** -0.85 ***
-0.31 -0.34 -0.19
- 0.41 - 0.14
0.02 -0.59 *
-0.39 0.34
0.33 -0.17
- 0.04 -0.55 *
0.03 -0.60 *
0.01 -0.72 **
0.10 -0.63 *
-0.10 - 0.38
-0.26
-0.77 **
0.17
- 0.06
-0.78 **
-0.56 *
-0.81 **
-0.78 **
- 0.03
-0.18 -0.14
- 0.47 - 0.45
- 0.02 - 0.01
- 0.00 -0.15
- 0.39 - 0.45
- 0.24 -0.53 *
- 0.43 -0.67 *
- 0.31 -0.88 ***
0.24 -0.38
-0.12 - 0.21
-0.34 - 0.64
0.11 0.26
0.20 -0.20
-0.30 -0.66 *
0.12 -0.70 **
-0.10 -0.83 **
-0.16 -0.76 **
0.46 -0.34
-0.35 - 0.27 -0.15
- 0.46 0.04 ~ 0.44
0.02 ~ 0.25 0.16
0.01 - 0.02 0.02
-0.58 * 0.06 -0.55 *
-0.65 * ~ 0.07 -0.54 *
- 0.66 0.03 -0.60 *
-0.91 *** - 0.03 -0.79 **
~ 0.23 - 0.06 0.16
~ 0.43
-0.68 **
0.10
- 0.02
-0.18
0.12
0.30
0.17
-0.13
- 0.50
0.28
-0.14
-0.78 **
-0.61 *
0.14
0.19
-0.78 ** 0.25
-0.81 ** 0.03
-0.23 0.11
-0.56 *
-0.50
-0.65 *
-0.51
- 0.22
*** PiO.001; * * P < 0.01; * P < 0.05.
TABLE II
Correlafion coefficients computed between Ihe CNV drfferentiation (Go-No Go) meawre and person&y (SHAPS and Eysenck) measures
in Table II. As may be seen, significant negative correlations were obtained between the Go/No Go difference measures and all measures of the Emotionality/Neuroticism factor (Hostility, De- pression, Anxiety and Introversion from the SHAPS, and Neuroticism from the EPQ), with high Emotionality subjects showing poor differ- entiation. However, this relationship was obtained at temporal sites but nof at the vertex. Psycho- ticism (P) showed a strong negative correlation with the Go/No Go difference at both temporal and central sites and for both CNV measures (CNV 11 and CNV 12). That is, high P scorers showed poor differentiation. Paradoxically, Vent correlated positively with Go/No Go difference at the vertex.
Go/No Go CNVs and self-report state measures (i) SACL measures. In Expt. 1 there were no
significant correlations between Go/No Go CNV and either stress or arousal on the SACL. In Expt. 2, however, some relationships were found be- tween CNV and state measures. Firstly, arousal measured following the Go/No Go session was negatively correlated with No Go CNV amplitude at the vertex: for CNV 11, r = -0.68, P < 0.01. That is, more aroused subjects tended to show lower amplitude No Go CNVs. Secondly, stress measured following the Go/No Go session was positively correlated with Go CNV amplitude at the temporal placements: for CNV 12 at T3, r = 0.71, P < 0.01; for CNV 12 at T4, r = 0.69, P <
0.01. That is, subjects who rated themselves as more stressed showed higher amplitude Go CNVs.
(ii) Task related measures In Expt. 1, Go CNV 12 at both C3 and C4 was positively correlated with reported task difficulty, concentration and tenseness during the task: correlations ranged from 0.54 (P < 0.05) to 0.70 (P < 0.01). That is, sub- jects who rated the task as more difficult, and their concentration and tenseness during the task as higher, tended to show higher amplitude Go CNVs. The final quarter of the No Go CNV (CNV 12) measured at the vertex was negatively related to alertness during the task (r = -0.58, P < 0.05). That is, low alertness was associated with high amplitude No Go CNVs.
-5 i
Fig. 4. Laterality index (left-right) for 12 CNV points in the Go and No Go conditions in Expt. 1.
In Expt. 2 self-reported alertness during the task was again negatively correlated with the No Go CNV (CNV 11) at both central and temporal placements: for Cz, r = -0.60, P < 0.05; for T3, r = -0.66, P < 0.05. The No Go CNV (CNV 11) at Cz was also negatively correlated with reported concentration during the task: r = -0.58, P < 0.05.
The Go/ No Go CN V and laterality There were no laterality differences for either
Go or No Go CNV (see Fig. 4). Nor was there any correlation between the laterality index for either Go or No Go CNVs and any of the personality measures. There were, however, significant rela- tionships between lateralization and state mea- sures. In Expt. 1, the laterality index for Go CNV (12) correlated positively with concentration (r = 0.66, P < 0.01) alertness (r = 0.50, P < 0.05) and tenseness (r = 0.50, P < 0.05). That is, subjects who rated their concentration, alertness and tense- ness as relatively high showed Go CNVs that were more clearly lateralized in the left hemisphere. In Expt. 2, where recordings were made from tem- poral placements, this pattern failed to emerge. Here lateralization of the Go CNV was negatively related to tenseness (r = -0.52).
DISCUSSION
A degree of circumspection must be applied in interpreting the results of this study, given the large number of correlations performed between CNV and psychometric measures and the conse- quent likelihood that some, at least, of the signifi-
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cant associations may be spurious. Nonetheless, a number of the correlations obtained, particularly between CNV and personality measures, were im- pressively high, and generally the results of the present study confirm, for normal healthy sub- jects, the association between differentiation of the Go/No Go CNV and impulsiveness previ- ously reported for mentally abnormal offenders (Howard et al., 1982). Our results are in agree- ment with Barratt’s recent report (1983) of an inverse relationship between impulsiveness and CNV amplitude. However, the precise relationship between personality and the Go/No Go CNV would appear to depend on electrode derivation. While poor Go/No Go CNV differentation at the uertex reflects a low Go CNV and correlates with general measures of impulsiveness (Imp and Vent from Eysenck and Eysenck’s 15, P from the EPQ), poor CNV differentiation at temporal sites ap- pears to correlate more with measures of emotion- ality (Hostility, Depression, Anxiety and Introver- sion from the SHAPS; Neuroticism from the EPQ). Our results confirm the promise that the Go/No Go CNV may be used as an objective electrocorti- cal measure of changes in emotionality and im- pulsiveness, for example cyclical changes associ- ated with the premenstruum in women (Howard et al., 1988). It also offers a promising approach to the medicolegal assessment of personality-dis- ordered offenders where loss of impulse control is thought to be an important factor contributing to their offending.
So far as subjective state is concerned, our results suggest that the Go CNV varies with sub- jective stress, higher Go CNVs being associated with relatively higher levels of stress, particularly at temporal sites. This agrees with results from a recent study by Brown et al. (1988) where positive correlations were obtained between Go CNV at temporal sites and both stress level and change in stress level, as indexed by the SACL, following verbal and visuospatial versions of a ‘match/mis- match’ task. However, this relationship between Go CNV and subjective stress appears to be non- linear. In studies investigating the effects of help- lessness-induced stress on the CNV (Howard et al., 1985), very high subjective stress was associ- ated with a reduction in Go CNV amplitude,
resulting in a loss of electrocortical differentiation. This agrees with the results of Glanzmann and Froehlich’s (1984) study, where they found poor Go/No Go differentiation associated with high state anxiety, at least in high trait anxiety subjects. In a recent study of Go/No Go CNV and cigarette smoking (Norton and Howard, 1988), changes in Go CNV amplitude with smoking were dependent on subjects’ initial stress level (as indexed by the SACL). High stress subjects showed a reduction in Go CNV with smoking, while low stress subjects showed an increase in Go CNV with smoking. As in the present study, subjective stress correlated positively with Go CNV amplitude overall.
Together, these results suggest that the Go CNV is an electrocortical index of activity in a neural system which mediates subjective stress. This sys- tem would correspond to the ‘Reward Motiva- tional System’ or ‘Go System’ in Howard et al’s (1982) model, which is said to mediate the Go CNV. Moderate levels of activity in this system would be associated with a high Go CNV and moderate degrees of subjectively experienced stress, while high levels of activity in this system would be associated with a reduction in Go CNV amplitude, possibly through secondary activation of the Aversive Motivational System (‘No Go System’), together with high levels of subjective stress.
Our results suggest that subjective arousal, as tapped by the SACL arousal measure and by self-reported alertness in the task, is inversely related to amplitude of the No Go CNV at both temporal and central placements. A significant relationship between changes in No Go CNV and changes in SACL arousal with smoking was found in the recent study by Norton and Howard (1988). Taken together, these results suggest that the neu- ropsychological system mediating the No Go CNV (Aversive Motivational System in Howard et al.‘s model) also mediates subjectively experienced arousal. Moreover, poor electrocortical differenti- ation might result from both high stress (high activity in the Reward Motivational System, re- sulting in low Go CNV), and/or low arousal (low activity in Aversive Motivational System, resulting in high amplitude No Go CNV). In the recent study of smoking and the Go/No Go CNV (Nor-
ton and Howard, 1988) the perception of con- tingencies was investigated in the Go/No Go task. Low perceived control over the aversive white noise was significantly associated with both low arousal and high stress. Thus both poor electro- cortical differentiation and low perception of con- trol over aversive stimulation may reflect dis- turbances in the neuropsychological systems mediating stress and arousal.
In Expt. 1 of the present study, the Go CNV showed no clear evidence of lateralization, notwithstanding the fact that all subjects were making a right-handed button press. Nonetheless, greater concentration, alertness and tenseness were associated with relatively greater left hemisphere activation, as indexed by a higher amplitude Go CNV at C3 relative to C4. This relationship ap- peared not to hold for the temporal electrode derivations, in Expt. 2. The greater left central activation indicates a greater motor readiness in those subjects who were more concentrated, alert and tense, and suggests that there is a neuropsy- chological dimension characterized, at one pole, by left central activation and reflected in high stress and high arousal; and at the other pole, by right central activation and reflected in low arousal and low stress. This dimension would correspond neatly to the balance between what Tucker and Williamson (1984) refer to as ‘activation’ and ‘arousal’ processes. These are said to be asymmet- rically represented in the brain, ‘activation’ being mediated by a dopaminergic mobilization of the left hemisphere, ‘arousal’ by a noradrenergic mobilization of the right hemisphere. The ‘activa- tion’ process is said to facilitate motor readiness and informational redundancy, while the ‘arousal’ process is said to facilitate orienting to novelty.
The above considerations led us to suggest the schema shown in Fig. 5, where primary (perceived threat) and secondary (perceived control) ap- praisal processes are represented as orthogonal dimensions. Poor Go/No Go differentiation is associated with low perceived control in conjunc- tion with either high perceived threat (anxiety stress) or low perceived threat (low arousal). The anxiety/stress dimension corresponds, in trait terms, with Emotionality/Neuroticism. Our re- sults suggest that neuropsychologically this dimen-
Fig. 5. Primary (‘perceived threat’) and secondary (‘perceived control’) appraisal processes represented as orthogonal dimen- sions. ‘ACTIVATION’ and ‘AROUSAL’ refer to processes said by Tucker and Williamson (1984) to be mediated by left and right hemispheres, respectively. SACL, Stress Arousal
Check-List of Mackay et al. (1978).
sion involves the temporal lobe. It is interesting to note that disturbances in emotionality are amongst the personality characteristics attributed to tem- poral lobe epileptics (Bear and Fedio, 1977).
Blackburn’s (1971) impulsivity and Eysenck’s Psychoticism dimensions would both correspond, in terms of the schema shown in Fig. 5, to the secondary appraisal (perceived control) dimen- sion, such that high Im/high P individuals should show, in addition to poor electrocortical differ- entiation, low perceived control over stressors. This supposition remains to be verified experi- mentally, but if supported would provide an un- derlying cognitive mechanism for these traits. The personality dimension orthogonal to Impulsivity, namely, Sociability (Blackburn, 1971) or Anxiety (Gray, 1982) would correspond to the primary appraisal (perceived threat) dimension shown in Fig. 4, since it is reasonable to suppose that so- cially anxious individuals have a high appraisal of threat, particularly interpersonal threat. This sug- gests that Gray’s Behavioural Inhibition System (BIS) (Gray, 1982), the supposed neuropsychologi- cal substrate of anxiety, mediates the primary appraisal process. It also suggests that the dy- namic balance between Tucker and Williamson’s ‘activation’ and ‘arousal’ processes may represent the cortical extension of Gray’s BIS in Man. This suggestion would be consistent with Gray’s atten- tional model of anxiety, according to which highly anxious subjects over-attend to cues signalling non-reward, punishment, etc. It would also be
44
consistent with Tucker and Williamson’s sugges- tion that hypervigilance and clinical symptoms of anxiety are associated with a predominance of the left hemisphere ‘activation’ process. This sugges- tion has found support in a recent study by Brown et al. (1988) in which a strong relationship was reported between social withdrawal and a relative left hemisphere (C3) mobilization in both verbal and spatial tasks.
Finally, our results and their interpretation have implications for the functional significance of the CNV. The CNV has traditionally been considered as a unitary phenomenon whose functional signifi- cance is to be explained in terms of a single psychological construct, such as ‘expectancy’ (Walter et al., 1964); ‘motivation’ (Irwin et al., 1966; Rebert et al., 1967); ‘conation’ (Low et al., 1966); ‘motor readiness’ (Jarvilheto and Fruehs- torfer, 1970; Rohrbaugh et al., 1976); ‘arousal/ attention’ (Tecce, 1972). Results of this and other studies suggest that the CNV should probably not be considered as a unitary functional entity. Thus, for example, in the same Go/No Go task para- digm, two distinct and unrelated slow potentials (Go CNV and No Go CNV) are elicited which each relates to different psychological processes (‘stress’ and ‘arousal’). Similarly, CNVs elicited in verbal and spatial versions of a ‘match/ mismatch’ task relate to distinct neuropsychological processes (Brown et al., 1988). Moreover, each of these task-specific CNVs has its own scalp topography, e.g. lateralization in right or left hemispheres (CNVs generated in spatial and verbal tasks, re- spectively) or non-lateralization (Go and No Go CNVs); amplitude reduction at temporal sites compared with central sites (Go CNV) or no reduction (No Go CNV). Thus we should prob- ably address questions of functional significance to particular CNVs generated in particular condi- tions and particular tasks, and recorded at particu- lar electrode derivations, rather than to ‘ the CNV’.
ACKNOWLEDGEMENTS
The authors are grateful to Brigitte Rockstroh and two anonymous reviewers for their helpful comments on an earlier version of this paper.
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