Date post: | 16-Dec-2015 |
Category: |
Documents |
Upload: | heather-evans |
View: | 218 times |
Download: | 1 times |
The cerebral cortex has four lobes, each is specialized for different activities.
• The lobes and some of their functions:– Occipital lobe- initial processing of visual input
– Temporal lobe - primary auditory cortex, integration of multiple sensory inputs, Wernicke’s area
– Parietal lobe - somatosensory processing. Each region of parietal cortex receives somesthetic and proprioceptive input from a specific body area, mostly from the opposite side of the body.
– Frontal lobe - voluntary motor activity, speaking ability (Broca’s area), and elaboration of thought. Stimulation of different areas of its primary motor cortex moves different body regions.
Frontallobe
Central sulcus
Parietallobe
Parietooccipitalnotch
Occipitallobe
Cerebellum
Brain stem
Temporallobe
Lateralfissure
Occipital lobe
Primary visual cortex
Wernicke’s area
Temporal lobe
Primary auditory cortex
Centralsulcus
Somatosensory cortex
Posterior parietal cortex
Wernicke’s area
Parietal lobe
Lefthemisphere
Cross-sectional view
Temporal lobe
Sensory homunculus
Primary motor cortex
Centralsulcus
Broca’s area
Frontal lobe
Premotor cortex
Lefthemisphere
Cross-sectional view
Temporal lobe
Motor homunculus
Centralsulcus
Parietal-temporal-occipitalassociation cortex
Limbic association cortex
Prefrontal association cortex
Association areas of the cortex carry out many higher functions:Association Areas of the Cerebral Cortex
planning for voluntary activity, decision-making,
creativity, and developing
personality traitsintegrates somatic,
auditory, and visual sensations from these three
lobes
involved with motivation, emotion, and
memory
Sensory input
Primary sensory areas(somatosensory, 1o visual, 1o auditory cortices)
Higher sensory areas
Association areas
Higher motor areas
Primary motor areas
Motor output
Fundamentals of Sensory Systems
A. General Concepts in Sensation and PerceptionFunction of sensory systemsVisceral versus sensory afferentsSensation versus perceptionPsychophysics
B Receptor Structure and FunctionSpecific for particular forms of energyVary across sensory systemsPerform common function (transduction) in unique waysSites of convergence and divergence
C. Peripheral OrganizationLabeled Line PrincipleTopographic projectionsMechanisms to enhance contrast sensitivity
• Central ProcessingIncludes sensory cortex and association areasResponse Maps and Plasticity
Variable perceptions from the same visual inputDo you see two faces in profile, or a wine glass?
Do you “see” a white square that is not really there?
Receptor Morphologies Reflect Specialized Functions
PhotoreceptorsMechanoreceptorsThermoreceptorsOsmoreceptorsChemoreceptorsNociceptors
CATEGORIES OF RECEPTORS
Receptor Potentials are GRADED
Generator potential: SomatosensoryReceptor potential: Auditory/Visual
Stimulus off
Slowly adapting
Stimulus on
Time
Receptorpotential(mV)
Stimulusstrength
Tonic ReceptorsMuscle Stretch, Proprioception
Stimulus off
Rapidlyadapting
Stimulus on
Time
Receptorpotential(mV)
Stimulusstrength
Off response
Phasic Receptorsskin touch
Doctrine of Specific Energyor
Labeled Line Principle
“Phantom”
Pain
Coding of Sensory Information
Stimulus Property Coding Mechanism
Stimulus Modality Distinguished by the type of receptor activated (what) and the specific pathway that transmits
this information to a particular area of (sensory)cerebral cortex
Stimulus Location Distinguished by location of activated receptive (where) field, and the pathway that is activated to
transmit this information to the area ofcerebral cortex representing that location.
Stimulus Intensity Distinguished by the frequency of action (how much?) potentials and the number of receptors
activated.
Receptor endingsof afferent neurons
Receptive fieldson skin surface
Receptive Field Size Determines Acuity
Sensory homunculus
Stimulated less Stimulated less
Stimulated most
Receptorpathways
Skin surface
Frequencyof action
potentials
Baselinelevel ofactivity
Location on skin
Mechanisms To
Enhance Acuity
Transmissionstopped
Lateralinhibition
Frequencyof action
potentials
Baselinelevel ofactivity
Area of sensation on skin
Transmissionstopped
Transmission continues
Center/Surround Organization of Receptive Fields
Sensory Pathways: CNS
Primary Sensory and Association Areas of Cerebral Cortex
Practical Applications