Maps of the MindMemory and Cognition Lecture 9

Electrophysiological

Haemodynamic

Cognitive Neuroscience Methods…

of seeing inside the box of tricks…

Psychophysiology

• Aim is to develop mind reading technologies

• We are most interested in the PPY of Perception and Cognition. In other words, Cognitive Neuroscience

• Can we tell what a person is thinking or experiencing just by looking at their brain activity?

Phrenology Was Odd…

• There is no known mechanism that would sculpt the contours of the skull according to underlying brain shape – i.e. there is no correlation between local contours of the

skull and the underlying size or shape of the brain

• Their psychological ‘model’ was based on common sense constructs of personality

– I.e. Looking in the wrong place for the wrong thing!

But not entirely wrong…

• The idea of functional localisation has survived, but in a different form

– Localisation does not respect character traits, like honesty, peevishness

– Localisation may respect, for example, sensory modality, ‘cognitive systems’ (e.g. LTM), along with other psychological mechanisms yet to be elucidated

Acceptable ‘modern’ principles of functional neuroanatomy

• Functional Segregation Discrete cognitive functions are localised to specific

parts/circuits of the brain (complex tasks are ‘divided and conquered’)

• Functional Integration Coordinated interactions between functionally specialised

areas (e.g. during retrieval from episodic memory, reading, perceptual binding etc)

Where We At?

• We want to read a person’s mind from the activity of their brain

• Their mind is composed of lots of interacting cognitive processes

• Each distinct process is carried out by networks of brain regions, each region is probably performing specific functions, but they all work together

• So we need a device or a technique that can detect changes in brain activity specific to any cognitive process

So What Do We Need?

• In an experiment we (think we) engage different functions in different conditions. For every condition we

– Detect rapid changes in neuronal activity (requires a temporal resolution of milliseconds, 1/100ths of a second)

– Locate activity within brain structures that are engaged (may require an anatomical (spatial) resolution of millimeters or better)

• Currently no such technique exists. Instead we rely on converging data from many techniques

Electrophysiological Techniques EEG

non-invasive recordings from an array of scalp electrodes

Averaging EEG produces ERPs

• Portions of the EEG time-locked to an event are averaged together, extracting the neural signature for the ‘event’.

10uV+

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TIME (sec)0 21

DOG

AIR

SHOE

AVERAGE

What do ERP waveforms tell us?

CONDITION A

CONDITION B

0 1 2

TIME (seconds)

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ONSET OF EVENT

INFORMATION ABOUT THE NEURAL BASIS OF PROCESSING IS PROVIDED BY THE DIFFERENCE IN ACTIVITY

Functional Inferences Based Upon Electrophysiology

Timing Upper limit on time it takes for neural

processing to differ Time course of a process (onset,

duration, offset)

Level at which a process is engaged

Engagement of multiple processes at different times or in different conditions

Early Topography

Late Topography