1

Introduction to Cognitive Neuroscience

Dr. Sukhvinder S. Obhi

Centre for Cognitive Neuroscience

Wilfrid Laurier University

2

Outline

• Historical Contextualisation

• Does Cognitive Psychology need the brain?

• Does neuroscience need cognitive psychology?

• Introduction to the study of Action

3

4

Epilepsy

• Epileptic seizures caused by spontaneous firing of neurons

• Can spread rapidly causing the body to convulse

• In extreme cases where people are suffering from recurrent seizures frequently, surgery may be considered

• The aim is to separate the source of the neuronal firing to stop it spreading

5

Wilder Penfield (1954)

Awake patient: http://www.youtube.com/watch?v=H4yhky5KIio

6

Penfield

• Stimulation to the occipital lobe: “a star came down towards my nose”

• Stimulation of another (motor) region: “those fingers and my thumb gave a jump”

• Temporal lobe: “I heard a radio” (memory)

7

8

Contextualisation

• Somehow, functional processes are embedded into the mass of tissue that we call the brain

• Traditionally the study of cognition included such topics as thinking, perceiving, imagining, remembering, speaking, and planning

• Cognitive neuroscience considers the same issues, but also from a neural perspective

9

Interdisciplinary Nature of CogNeuro

Cognitive Neuroscience

Anatomy

Neurophysiology

Psychology and Neuropsychology

BiologyPhysics

Computer Science

Neurology

10

Cognitive Neuroscience• The study of the neural basis of cognition

Pinel (2006)

• The field of cognitive neuroscience concerns the scientific study of the neural mechanisms underlying cognition and action and is a branch of neuroscience. Cognitive neuroscience overlaps with cognitive psychology, and focuses on the neural substrates of mental processes and their behavioral manifestations. The boundaries between psychology, psychiatry and neuroscience have become quite blurred. Cognitive neuroscientists tend to have a background in experimental psychology, neurobiology, neurology, physics, and mathematics.

adapted by S.S. Obhi from wikipedia*

*(never use wikipedia as a single reference source – always cross check the information before citing it and provide other refs!!)

11

Why interdisciplinary?

• Theory and methods of Cognitive Neuroscience are often very complex

• Individuals with different types of training collaborate to make it happen

• All good fMRI (brain imaging) centres have a Physics group that works with “experimental psychologists” to optimize the scanning methods for various types of research

• A great example of how researchers interested in a common topic can work together more usefully than working alone!

12

Brain imaging webpage

Psychologist

Mathematician

MD

PhysicistNeurologist

13

History

• During most of history humans were too busy to think about thought!

• “Thought about thought” may have come about at the stage in history where day-to-day survival did not occupy every hour of every day

• Probably linked to the beginnings of farming and domesticating animals etc

14

Historical Perspective

• Long history of interest in how the brain creates our mental world

• Central question: how does the physical substance of the brain give rise to our feelings, thoughts, emotions and actions?

• Historically referred to as the mind-body problem

15

Descartes & Dualism• Rene Descartes (1596-1650) was an

early proponent of dualism

• Mind non-physical and immortal, body physical and mortal

• They interact in the pineal gland in the centre of the brain

• According to Descartes, sensory stimulation would cause vibrations in the body/brain that would be picked up by the pineal gland which would generate a non-physical sense of awareness

16

Critics of Descartes

• Spinoza (1623-1677)

• Mind and Brain were just two different levels of explanation for the same thing – but not two different things

• Termed Dual-Aspect Theory – still popular today

17

Levels of Explanation

• This is a useful concept

• Can explain phenomena at the cellular level, at the neuronal population level and at the behavioural level

• One of the goals of the scientific study of mind and brain is to understand how things at one level are related to things at another

18

Reductionism• A popular approach to the mind-body problem

• Cognitive, mind based concepts are currently useful but they will eventually be replaced by biological constructs (just as much of physical chemistry can be reduced to physics)

• So emotions, thoughts, desires etc, will be described simply as patterns of neuronal firing

• Many believe this is too extreme – there must be some validity in our own sense of “self”, perhaps over and above the physical working of the brain

• Pure reductionist view sometimes called “materialism”

19

Cautionary Examples

• Understanding individual liver cells is not enough to gain an understanding of liver function

• Similarly, understanding atoms in a solid, does not tell you about the properties of the macroscopic solid

• Understanding the hardware of a computer is insufficient to understand the jobs a computer performs

• To believe fully in reductionism is to believe that low level processes always fully explain high level processes

20

Scientific Approaches to Mind & Brain

• Thought started very early, Ancient Greece (if not before that!)

• Aristotle (384-322 BC) noted that the ratio of brain size to body size was greatest in more intellectually advanced species (humans)

• But wrongly thought that cognition was centered at the heart and that the brain was a cooling system

• Note: Roots of much of psychology (and therefore cognitive neuroscience) are in Philosophy

21

Egyptian Contributions

• Ancient Egypt – scientists had access to condemned criminals

• There are reports that scientists actually vivisected these people (note: to vivisect is to dissect, cut or perform surgery on a living animal)!!

• In this age speculation that the brain controlled different behaviours emerged – but wrongly placed emphasis on the ventricles (cavities in the brain)

22

Roman Contributions

• Galen – a surgeon who worked on gladiators

23

Roman Contributions

• Galen (AD 130-201) thought that war and Gladiator games were the greatest school of surgery

• Identified many major structures in the brain

• Also credited for observing that nerves project to and from the brain

• But was misguided in thinking that mental experiences arose out of the ventricles – an idea that went unchallenged for 1500 years!

24

Rene Descartes (1596-1650)

• Non-physical mind interacts with brain through pineal gland

• Often referred to the flow of “spirits” through nerves

• Compared to mechanical contraptions of his time

• Mind-body dualism

25

Lack of interest in the cortex

• Old pictures of the brain are interesting since they tended to draw the ventricles in exquisite detail and then just crudely draw the cortex!

26

Luigi Galvani (1737-98)

• Applied electrical currents to motor nerve and made frog’s legs move

• Linked electricity to the functions of the nervous system

• But wrongly thought that nerves and muscles contained an “electric fluid”

27

Golgi & Cajal

• Battle between 2 neuro-anatomists in Italy & Spain

• Golgi (1843-1926) developed a staining technique that could stain individual neurons

• Cajal (1852-1934) went on to show that individual neurons were discrete entities – and that neural matter was not a continuous mass of processes

28

Golgi stained neurons

29

Insights into Morphology

• Morphology = study of the structure of biological organisms

• Many early contributions were based on dissections and really attempted to inform knowledge of structure

30

Shift to cortical interest & functions

• Gall & Spurzheim (1810) – their drawings started to focus on the cortex a bit more

• Gall was a proponent of phrenology – localization of “traits” in the brain

31

The birth of Psychology

• Only really happened toward the end of the nineteenth century

• In a sense, it took the emphasis of the study of the mind away from its biological roots

• This was necessary since the topics of interest to early psychologists (James, Wundt etc) included such things as consciousness, attention and personality

• Biological study of the mind had, until this time, very little to say about these issues

32

Early Psychologists

William James (USA)

Wilhelm Wundt (Germany)

Sigmund Freud (Austria)

33

The gap between Psychology & Biology

• It is possible to make coherent and testable theories about cognition (mental processes) without referring to the brain

• Cognitive Psychologists have done this since the formation of the discipline - taking the “information processing approach” to cognition

• What are the processing steps underlying various mental phenomena?

• Use the computer metaphor in which the brain is analogous to a computer

34

Computer Metaphor

• The brain is like a computer - popularized in the 1950s coincident with the invention of the computer

• Famous model that uses this framework is Broadbent’s model in which perceptual processes are followed by attentional processes which move information into short-term memory

35

Box and Arrow models

Extraction of “physical” properties

Extraction of “abstract” properties

FilterIncoming

Stimuli

•A sequence of processing stages

•Implication of these models was that you could understand the steps needed to perform a certain task without reference to the brain

•Much as you can figure out how a computer program works without reference to the hardware

36

Processing not always sequential

• Important concept in the cognitive approach is that it is possible to have parallel processing

• Stages of processing can be interactive meaning that higher level processes can begin before low level processes are completed

• E.g., Early feature extraction and two visual systems

• Back projections in vision

37

Box and Arrows and Neural Nets

StimulusStimulus

identification

Response

selectionResponse

INPUT PROCESSING OUTPUT

38

Top Down Processing

• These models also emphasize how higher level processes can influence lower level processes

• Many attentional cueing paradigms work on this idea

• A cue primes the lower level perceptual processes to expect something in particular

• Shows itself as a faster response in trials that had a cue versus trials that didn’t

39

Example: Cueing Effects

Posner (1980)

40

The Birth of Cognitive Neuroscience

• Much influenced by the development of imaging techniques which allow observations of the working brain

• In the past (phrenology, neuropsychology etc) had to wait until a person died to examine their brain

• Also largely correlated with the fall of behaviourism and the general acceptance that a search for cognitive processes had to be undertaken

• Gazzaniga, an influential proponent of Cognitive Neuroscience claims that the term “Cognitive Neuroscience” was coined in a New York City taxi in the late 1970s

41

Methods

• Present day Cognitive Neuroscience is composed of a variety of methods

• Generally, the methods available to the cognitive neuroscientist can be placed on a number of dimensions

42

Considerations

• Temporal resolution: refers to the accuracy with which one can measure when an event is occurring

• Spatial Resolution: refers to the accuracy with which one can measure where an event is occurring

• Invasiveness: refers to whether or not the equipment is located internally or externally

43

Methods

Some cognitive neuroscience techniques

44

Does Cognitive Psychology need the brain?

• My experience at a Cognitive Science conference – still a divide between strict “box modellers” and people who consider it important to know about the brain

• An important question asked by Coltheart (2004)

• “Has Cognitive Neuroscience, or if not, might it ever (in principle or even in practice) successfully use data from cognitive neuroimaging to make theoretical decisions entirely at the cognitive level (e.g., to adjudicate between competing information processing models of some cognitive system)?”

45

Question:

• Does visual recognition of words and letters involve computing a representation that this independent of case?

Case example

46

Different case priming experiment

Both reaction time and imaging measures are giving different information about the same process – useful (?)

47

Does imaging just tell us where something happens?

• Many people would argue that it does

• But, the more we know about the systems that are engaged in the brain when performing different tasks, the more fully we will understand how the system works

48

Furthermore

• One source of information will never give us the full picture

• In order to understand the processing mechanisms and their biological basis we need more information

• For example……

49

• Inputs and outputs to the fusiform

• Cytoarchitechtonics* of the processing route

• Neurotransmitters in the processing route

*cellular structures

50

Triangulation & Converging Evidence

• The use of multiple sources and methods to address a common issue

• By comparing results using different methodologies a holistic understanding of the phenomenon under study may be achieved

• This is very much in the spirit of understanding how to link evidence from cognitive neuroscience with theories and concepts from cognitive psychology - mutually informative and complimentary

• (Even though you will come across people who are in ‘one camp’ or another) - OPINIONS are allowed!!

51

Example • Cognitive Psychology evidence favors parallel search in word

recognition, not serial

• But it does not give us any clues as to why – in fact computer programs can recognize words by both serial and parallel search

• The reason why might be linked to the relatively slow neural response time – we only know this because people have measured neural response time

• In this way, information from studies of the processing taking place in the brain can help to put biological constraints on otherwise unconstrained cognitive models

52

Does Cognitive Neuroscience need Cognitive Psychology?

• We’ve known that things like perception, remembering, pain, mood and sexual desire are all products of processing going on in the brain for a long time (19th century)

• The methods of Cognitive Neuroscience make it possible to study these processes in vivo – this makes for tantalizing headlines in the media

53

Media Frenzy due to in vivo observations

54

55

But

• Cognitive Neuroscience techniques by themselves are not useful without carefully designed experimental paradigms that have stood the test of time and the criticism of researchers

• These paradigms are often the paradigms developed by cognitive psychologists

• Without this knowledge gained over decades of research in cognitive psychology, imaging might not be anything more than the new phrenology

56

What do you see?

• In an imaging experiment you typically observe changes in blood flow

• Your job however, as a cognitive neuroscientist is to relate these observations to the well established concepts of cognitive psychology

• For example, how does activity in the medial temporal lobes contribute to different types of memory as identified over many years by cognitive psychologists?

57

Essential Reading

• Ward book Chapter 1 (relates to today)