Shantanu Ghosh
IIT Delhi
An Introduction to Cognitive Neuroscience
The Brain
Central organ for control of body’s activities: receives information from peripheral organs via afferent neuronal pathways; controls various organs via efferent pathways
Not restricted to physical movement or control of organs, but includes energy metabolism
Separated from GC by the blood-brain barrier
Works by neurotransmitter release, consumes energy
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Cerebellumpons
medulla
Churchland & Sejnowsky, 1988, Science 242
Patch Clamp
Fluorescent dyes
Damage in Broca’s area
Damage in Wernicke’s area
Ojemann & Whitaker (1978): cortical stimulation“common sites for naming in L1 and L2”, “specific sites for naming in L1 and L2”
L2 more variable and extended representation than L1
Fox et al. (2006) PNAS USA 103, 10046-10051
Intrinsically defined dorsal and ventral attention systems and the overlap between them
Cannestra et al. (1998) J Neurophysiol 80:1522-1532
Time course of Calcium transient signaling
Frostig et al. (1990) PNAS USA 87
Comparison of OD maps, rCBV and oxygen delivery changes
activation
baseline
Donders subtraction method
[A + B] – [B] = A
Functional map
TONGUE LIP HAND ELBOW
SHOULDER HIP KNEE ANKLE
Ghosh et al., unpublished data
Mapping the sensorimotor areas
S RSensory information
Hemodynamics- rCBF, rCBV, BOLD
Voltage distribution
Connectivity
Metabolic pathways for information transfer (ion transport, biochemical pathways, etc)
3 Major Challenges of Cognitive Neuroscience
2 What are the stimuli to be used in the experiment?
3 How do we interpret the data?
1 What are the hypotheses to formulate?
Conceptual framework for a cognitive model
NEURAL STRUCTURES 2A
NEURAL STRUCTURES 1A
NEURAL STRUCTURES 2B
NEURAL STRUCTURES 1B
Object image
f1 f2 f3 … fnFeature extraction level(Early sensory cortex)
Processing LevelCortical Level 1
Representational level(Intermediate Cortical level 2)
Central Processes(Non-sensory Cortical levels)
Higher order global processes (Attention, memory, perception, etc)
Object
• Technological advances in imaging and genetics allow the study of the neural activity-behavior interface
• A model has to be predictable and replicable in order to lend itself to study
Researching the relation between neural activity & behavior
Forced Normalization- A Putative Model
• “Forced Normalization is the phenomenon characterised by the fact that, with the occurrence of the psychotic states, the EEG becomes more normal or entirely normal as compared with previous and subsequent EEG findings”
• Put more crudely, “there would seem to be epileptics who must have a pathological EEG in order to be mentally sane”
Landolt 1952, 1958
Glutamate, GABA and Forced Normalization
GABA GLUTAMATE = PSYCHOSIS
GABA GLUTAMATE = EPILEPSY
Levels of analysis
from the outside; behavioral systems
behavior to brain regions
activity of neurons in networks
structure and connectivity of sub-cellular membranes and systems
Psychology/Linguistics
Neuropsychology
Neurophysiology
Molecular/Cellular and Biophysics
The homunculus
Mapping the sensorimotor areas
TONGUE LIP HAND ELBOW
SHOULDER HIP KNEE ANKLE
Ghosh et al., unpublished data
Auditory retrieval of letter names in sequence
Singh & Ghosh (2006)
R MOG (BA 18/19, 28, -86, 4),
R lingual gyrus (BA 18, 4, -84, 2)
L,R cuneus (BA 18/19, -14, -90, 24 and 14, -88, 24)
R posterior cingulate gyrus (BA 23, 2, -62, 14)
L precentral and lingual gyri (BA 4/1, 17/18)
L MFG (BA 10/6, -48, 0, 50 to –38, 60, 12)
L,R SPL (BA 7)
R lingual gyrus (BA 18)
Lexical
Structural-functional
Concept association
Results 2Results 2
Watkins et al 2001 Cereb Cortex
SPM{F}
Neurometric functions:Neurometric functions:Responses to stimuli of increasing duration and complexityResponses to stimuli of increasing duration and complexity
0 exposure duration {ms} 8000 exposure duration {ms} 800
Adaptation of Adaptation of neuronal responsesneuronal responses
AttentionalAttentionalmodulationmodulation
time{ms}time{ms}
Context-sensitive responsesContext-sensitive responses
timetime stimulus nstimulus nstimulus n-1stimulus n-1 stimulus n+1stimulus n+1
response nresponse n
interaction between stimuliinteraction between stimuli
Interactions and context-sensitive effectsInteractions and context-sensitive effects
Context 1Context 1(PARAM absent)(PARAM absent)
Context 2Context 2(PARAM present)(PARAM present)
without A & with Awithout A & with A(e.g.. recognition)(e.g.. recognition)
11 22
4433
A 2 x 2 layoutA 2 x 2 layout
task 1 2 3 4task 1 2 3 4
interaction effectinteraction effect (A x Context)(A x Context)
AA
AA
Context 1Context 1 Context 2Context 2
Thank you!