F25 - Neural Correlates of Cognition

Neuroscience Investigations Logic - Part 1

All brains

• One size fits all → NO -

• All brains slightly different (even with general guideposts) – Like snowflakes

All cognition

• Everyone does not think same way - think about this in terms of styles of thinking (visual, verbal, etc)

How do we deal with it

• Research

• Clinical

Neuroscience Investigations Logic - Part 2

Multiple techniques used to assess

• Assumptions

• Limitations

Choose technique with these issues in mind and what you want to investigate

— In our case, cognition and how brain encodes

Cognitive-Anatomic Organization - Part 1

Goal: Link COGNITIVE operations or units to anatomic regions - there’s really not a lot of zones to map out core cognitive faculties (ex: love, virtue, flag burning lmao)

ANATOMIC or spatial extent

• Extremes

  • Discrete, independent units - can’t make sense of complex functions like language (even looking for a word!) or general concepts

    • Look up Jeff Hinton on AI and concept coding

  • Distributed network - not really accounting for some functional units (ex: hearing can go out of your system and you’re still ok 😄 )

Scale of size

• What is the resolution of your anatomic unit from the instrument used for measurement

Brodmann’s Areas

Stupid and useless for the free world lmfao

Cognitive-Anatomic Organization - Part 2

COGNITIVE units

Parcellate cognition into components

• Functions/processing - this is doing stuff with representations (That color is tope, what’s the best thermos) - less variability

• Representations - I fucking love Mauve :D - more variability

Evolving concepts

• Better define cognitive components/operations that can be supported neurally

Cognitive-Anatomic Organization - Part 3

Examples of cognitive functions/ processes in the brain that map onto neuronal functioning

• Selection, inhibition (in-laws lol), abstraction, integration, search, decide, link, etc.

Operations have been more simply assigned than in the past

– Resemble functions that can be supported in electrical circuit-like concept

Cognitive-Anatomic Organization - Part 4

These cognitive functions/processes can be of two main varieties

• Domain general – these functions are available across all types of cognition

  • e.g., inhibit any incorrect responses for any task

• Domain specific – functions only available to one cognitive domain

  • e.g., access to the phonological lexicon

Cognitive-Anatomic Organization - Part 5

Examples of cognitive representations in the brain that map onto neural substrates

• Category label, verbs

Need to be thought of still in neural circuits like electrical circuits

Typically, are not domain general but are domain specific

Cognitive-Anatomic Organization - Part 6

ANATOMIC units

• Range

  • Discrete, independent regions as a unit

  • Distributed network

• Designation of location

  • Brodmann area

  • Gyrus

    • Using gyral location as general grid is common

Cognitive-Anatomic Organization - Part 7

CAUs

• Cognitive-Anatomic Units (CAU): A delineated cognitive function/representation that is consistently associated with an anatomic region

  • Association is localized to the same sized anatomic region in the same location across individuals

Cognitive-Anatomic Organization - Part 8

CAUs

• Not all cognitive operations can be encapsulated as CAUs

• Some cognitive operations are “distributed” over multiple discrete anatomic regions, OR

• “Distributed” over a diffuse network of neural components

• Not all anatomic regions have specific cognitive operations associated with them

In this course, going to focus on CAUs

Neuroscience Investigations Logic - Part 1

Logic of how to localize CAUs

• Subtraction logic

• Activation logic

  • Essential

  • Involved

Neuroscience Investigations Logic - Part 2

Subtraction studies or logic

If remove a brain structure that is a CAU, then by subtraction logic

• → it should result in an impairment in the cognitive function assigned to the CAU

  • if not, then the cognitive function is wrongly delineated or there is no specific cognitive function essentially located in that brain regions

Neuroscience Investigations Logic - Part 3

Subtraction logic

• This logic was the basis for the classic Lesion Model that formed basis of neurologic localization

• Originally, test someone prior to death

• Assess their deficits in great detail

  • Die of unrelated cause

• Autopsy find what region is missing

• Deficit designates the cognitive function that was associated with the missing brain region

Neuroscience Investigations Logic - Part 4

Subtraction logic

• Extended the approach to strokes once imaging technologies developed

  • Stroke occurs

  • Test someone after the stroke to define deficits in detail

  • Obtain an image of the brain and associate the function lost with the deficit to the damaged brain region

Neuroscience Investigations Logic - Part 5

The “subtraction” that is typically used is a lesion – stroke, trauma, tumor, etc.

Problems

• Recovery of function and re-organization

• All brains different so how consistent are localizations of cognitive units across multiple individuals

• Lack of independence of cognitive units

Neuroscience Investigations Logic - Part 6

Activation studies and use of subtraction logic for localization of function

• Task-related PET or fMRI are examples

• Typically, these show all brain regions

engaged in performing a task or cognitive

component

• Includes regions

• Involved in performing the task, including those

• Essential to performing the task

Neuroscience Investigations Logic - Part 7

Activation studies

To confirm which anatomic region detected in an activation study is clearly essential to a cognitive operation

• Look at related lesion studies showing that “removal” of a brain region results in a consistent impairment, to some degree, of that cognitive operation

• Does not have to be a complete abolishment of the function, but a consistent reduction

Subtraction Logic

For functional imaging studies, this logic works best if the tasks that are being used to test for a loss of a cognitive function are

• One that consists of only that one cognitive function

  • • Typically though, a task has multiple cognitive

  • components

  • • How those components interact with each other

  • can dictate how well logic works

If comparing two tasks, they should only differ by the function targeting

Neuroscience Investigations Logic - Part 8

CAUs can assume a variety of roles

• An isolated unit that entirely and exclusively performs a given operation

  • A unit that performs an operation but other regions can independently do also

• A unit that works in conjunction with another unit to perform an operation

  • Synergistically or each does different suboperations that combine

• A unit that works in a network with multiple other regions together to perform an operation

Neuroscience Investigations Logic - Part 9

Looking at how CAUs interact with each other to perform a task depends on processing between units

Type of processing involving CAUs in networks

• Serial

• Parallel

• Cascade

Serial Processing

Type of processing

• Serial

  • Early PET

  • “Sternberg” serial processing logic

  • Assumption: Independent cognitive modules

  • Each unit must complete its processing entirely before send output to the next unit, which waits idly to that point

Subtraction Logic – Serial Processing

Type of processing

• Serial

• If two strings compared

• One has same modules and another has same plus one more

• Subtract two and find the one unit

Problems

• Not independent modules

• Likely interactive

• Remove one → not same as just subtract

• Recover

• Adapt

• Alternate pathways

Parallel Processing

Parallel processing

• Multiple brain modules working in unison

• Independent?

• Can send partial or final output from any module to any other module at any time during task performance

Problems

• Likely not independent

• Difficult to monitor

• Very difficult to hypothesize

• Not often match with the data

Cascade Processing

Cascade processing

• Processing occurs in multiple modules

• There is an order to the modules so not all connected to each other

• Not independent

• Each can inform the other with partial information and/or final information when completed processing

Subtraction Logic – Cascade Processing

A hybrid between serial and parallel

• Hypothesized that might be most common in the brain

Problems

• Not just blurring of serial and parallel

• Still difficult to hypothesize findings if lesion

Neuroscience Investigations Logic - Part 10

Subtraction logic with any type ofprocessing

• Problems with all

• What about representations?

• What about combinations of processing?

• What about modality dependence or independence?

Lesion Deficit Logic

Then why use?

There are clear cases where it works

Provides a basic framework of consistent associations that more complicated constructs and networks may be built upon - also helpful for efficiency

Different Aphasias, Apraxias, Alexias

Really important to note the power of language (interesting to think about thinking w/o language)

Lichtheim Model

An interesting loop on how concepts are related to audition, speaking, and other early cognitive concepts. Created the first model of motor-speech areas.

Wernicke and Broca start working

General picture of the brain’s anatomy

Modern brain model in the 90’s

Newer models of white matter

Aphasia

Aphasia – impairment of language functions

• Not just speech which is dysarthria

APPROACHES

• Disconnection

• Cognitive neuroscience

Disconnection Approach - Aphasia - P1

Set of symptoms traditionally assessed

• Fluency

• Comprehension

• Repetition

• Naming

Symptoms not associated with a single, specific region

• (e.g., not a naming center)

Disconnection Approach - Aphasia - P2

Disruption of symptoms

• Fluency

• Phonemic paraphasias

• Semantic paraphasias

• Neologisms

• Perseverations

• Stereotypical utterances

• Echolalia

• “Broca’s-like” halting speech

• Dysprosodia

Disconnection Approach - Aphasia - P3

Disruption of symptoms

• Comprehension

• Single word

  • Matching word to picture

• Sentence level – syntax and semantics

• Grammatical markers, nouns, verbs can differ

• Repetition

• Sentence

• Single words

• Differentially impaired compared to other components

• Naming

• Impaired in most aphasic syndromes

• Fluents - substitute words, paraphasic errors, circumlocutions

• Nonfluents – struggle to find, circumlocution

Disconnection Approach - SYNDROMES

• Broca’s aphasia

• Wernicke’s aphasia

• Conduction aphasia

• Anomic aphasia

• Global aphasia

• Transcortical motor aphasia

• Transcortical sensory aphasia

• Isolation of the Speech Area

Lesion Deficit - Disconnection (KNOW IT)

Thrombotic strokes usually cause these specific deficits

Broca’s Aphasia - will be asked this (have syntactic comprehension problem)

• Halting, ‘crunching’ speech in terms of fluency

– Do not produce function words

– Repetition and naming parallel speech fluency

• May have impairment in syntactic comprehension

• Requires large left perisylvian lesion that includes the operculum (Broca’s area), insula, and surrounding white matter

A LESION OF BROCA’S AREA IS NOT SUFFICIENT TO CAUSE BROCA’S APHASIA, NEED A TON MORE (WHITE MATTER, INSULA, ETC)

Wernicke’s Aphasia

• Fluent, paraphasic speech that makes no sense with neologisms, paraphasias

• Comprehension markedly impaired

• Circumscribed lesion of posterior superior temporal gyrus

• Usually a fairly transient state

• Evolves into anomic aphasia

• Partial lesions of posterior, superior temporal lobe → better outcome

• If include more than 50% of this region, poorer outcome

Conduction Aphasia

• Relatively more severe impairment in repetition as compared to conversational fluency

• Use to believe that disruption of white matter connection (arcuate fasciculus) between Wernicke’s and Broca’s area was the lesion

Recent studies show lesion in arcuate fasciculus is neither necessary or sufficient for conduction aphasia

• Only need lesion to most posterior area of the superior temporal lobe that projects to Broca’s area to get conduction aphasia

Many debate if this condition actually exists

• Needed for model but rarely is ever seen in pure form

Anomic Aphasia

• Fluent, substitute filler words for target words, semantic and occasionally phonemic paraphasic errors, circumlocutions

• Mild comprehension issues

• Lesion usually includes supramarginal and/or angular gyrus, or - ON TEST

• Mild involvement of posterior superior temporal gyrus

• Wernicke’s aphasics typically recover to be anomic aphasics

Global Aphasia

• Impairments in all domains

• Extensive lesion throughout perisylvian area → posterior inferior frontal, insula, underlying white matter, inferior parietal lobe, posterior superior temporal gyrus

• Occasionally, evolve into Broca’s aphasia typically

Lesion Deficit - Disconnection

• Transcortical motor aphasia

• Transcortical sensory aphasia

• Isolation of the speech area