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Ghosh et al., unpublished data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!