Cognitive Operations

• What does the brain actually do?

• Some possible answers:– “The mind”

– Information processing…

– Transforms of mental representations

– Execution of mental representations of actions

First Principles

• “cognitive operations are processes that generate, elaborate upon, or manipulate representations”

– As patterns of activity in one or more neurons

– We often lack conscious access to these representations

– Neuroscientists still know very little about how information is represented in the brain

Mental Representations

• Mental representations can start with sensory input and progress to more abstract forms

– Local features such as colors, line orientation, brightness, motion are represented at low levels

How might a neuron “represent” the presence of this line?

Mental Representations

• Mental representations can start with sensory input and progress to more abstract forms

– Local features such as colors, line orientation, brightness, motion are represented at low levels

Mental Representations

• Mental representations can start with sensory input and progress to more abstract forms

– texture defined boundaries are representations arrived at by synthesizing the local texture features

Mental Representations

• Mental representations can be “embellished”

- Kaniza Triangle is represented in a way that is quite different from the actual stimulus

-the representation is embellished and extended

Mental Representations

• Mental Representations can be transformed

– Rubin Vase, Necker Cube are examples of mental representations that are dynamic

Mental Representations

• Mental Representations can be transformed

– Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process

Mentally rotate the images to determine whether they are identical or mirror-reversed

SAME MIRROR-REVERSED

Mental Representations

• Mental Representations can be transformed

– Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process

Mental Representations

• Mental Representations can be transformed

– Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process

Mental Representations

• Mental Representations can be transformed

– Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process

Mental Representations

• Mental Representations can be transformed

– Shepard & Metzlar (1971) mental rotation is an example of transforming a mental representation in a continuous process

– The time it takes to respond is linearly determined by the number of degrees one has to rotate

– Somehow the brain must perform a set of operations on these representations - where? how?

Mental Representations

• Mental Representations can be transformed into abstract information representations

– Posner letter matching task

– Are these letters from the same category (vowels or consonants) or are they different?

Mental Representations

• Mental Representations can be transformed into abstract information representations

– Posner letter matching task

– Are these letters from the same category (vowels or consonants) or are they different?

– Are they physically the same or are they the same in an abstract way - they are in the same category?

A A

A a

A U

S C

A S

SAME

DIFFERENT

Mental Representations

• Mental Representations can be transformed into abstract information representations

– Posner letter matching task

– Participants are fastest when the response doesn’t require transforming the representation from a direct manifestation of the stimulus into something more abstract

Mental Representations

• Mental Representations can be representations of actions

– response selection and response inhibition

– when one of several responses is required, each response is pre-programmed and the appropriate one is selected

– In Go/No-Go tasks when the same response is made repeatedly on Go trials its representation is difficult to override on No-Go trials

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

RED

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

BLUE

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

GREEN

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

RED

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

BLUE

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

GREEN

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

GREEN

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

GREEN

Mental Representations

• Mental Representations can interfere

– Stroop task: name the colour in which the word is printed (I.e. don’t read the word, just say the colour

– The mental representation of the colour and the representation of the text are incongruent and interfere

– one representation must be selected and the other suppressed

– This is one conceptualization of attention

Mental Representations

• These are some examples of how a cognitive psychologist might investigate mental representations

• The cognitive neuroscientists asks:

– where are these representations formed?

– What is the neural mechanism? What is the code for a representation?

– What is the neural process by which representations are transformed?

First Principles

• What are some ways that information might be represented by neurons?

First Principles

• What are some ways that information might be represented by neurons?

– Magnitude might be represented by firing rate– Presence or absence of a feature or piece of information might

be represented by whether certain neurons are active or not – the “labeled line” theory

– Conjunctions of features might be represented by coordinated activity between two such labeled lines

– But these are just brainstorming suggestions…little is known about how information, especially complex representations and representations in memory are actually encoded

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