Methods of Cognitive Neuroscience

1
Methods of Cognitive Neuroscience

• Meghan Roarty
• University of California, Santa Barbara

2
What is Cognitive Neuroscience?

• The study of the brain mechanisms, the neural
  substrates, underlying various cognitive
  processes, such as memory, perception, attention,
  and language
• marriage of neuroscience and cognitive psychology
• Goal To link brain activity to behavior

3
Methods of Cognitive Neuroscience

• ? Patient Studies
  ? Electrophysiological Studies ?
  Neuroimaging Studies

4
Methods of Cognitive Neuroscience

• ? Patient Studies
  ? Electrophysiological Studies ?
  Neuroimaging Studies

5
Patient Studies

• Brain damage lesions, surgery, or focal injury
• Brocas aphasics
• Diseases Developmental Disorders
• Alzheimers Patients, Autistic Individuals
• Special cases
• Split-Brain Patients

6
Experimental Design Problems in Testing
Brain-Damaged Patients

• Experimental Group
• Hippocampal brain injury
• Control Group
• No brain injury
• Participants matched for age, education level,
  intelligence
• Run a study on the acquisition of spatial
  information on both groups and find that
• Hippocampal patients perform significantly
  worse than normal controls on a recall test of
  spatial knowledge

7
Experimental Design Problems in Testing
Brain-Damaged Patients

• ? Can we conclude that poorer performance is due
  to hippocampal brain injury?
• Nonequivalent control group
• Problem selective
• differences between two
• groups
• likely there are things inherently different
  about those who have suffered brain injury

8
Experimental Design Problems in Testing
Brain-Damaged Patients

• Experimental Group
• Hippocampal brain injury
• Control Group
• ? No brain injury
• 2nd Control Group
• other type of brain injury
• About as well as a Patient study can be
  controlled

9
Patient Studies Goal To link brain activity to
behavior

• Hippocampus
• important in the acquisition and retrieval of
• spatial knowledge
• Patients with damage to the hippocampus (Patient
  E.P.) have difficulty acquiring new spatial
  information about their environment

10
Patient Studies Linking brain activity to
behavior

• Language Areas in the brain

Brocas aphasia Damage to Brocas area causes
problems in language production Wernickes
aphasia Damage to Wernickes area causes
problems in language comprehension
Findings support Modularity of
Function ?Specific areas of the brain
responsible for specific functions
11
Patient Studies

• Advantage
• Direct link between brain and behavior
• Disadvantages
• Selective differences
• Difficult to find good controls
• Extent of damage
• Cognitive process may be affected by damage
  located elsewhere

12
Methods of Cognitive Neuroscience

• ? Patient Studies
  ? Electrophysiological Studies ?
  Neuroimaging Studies

13
Electrophysiological StudiesEvent-Related
Potential Recordings (ERPs)
ERPs small electrical changes in brain
associated with sensory or cognitive events
14
Electrophysiological StudiesEvent-Related
Potential Recordings (ERP)

• EEG electrodes placed on scalp ? signals
  amplified ? can observe voltage fluctuations
• Reflects brains global electrical activity
• Use simple averaging process, leaving you with
• ERP waveforms tied to specific neural processes

15
Electrophysiological Studies
An averaged ERP waveform consists of a set of
and - voltage deflections (peaks) Each peak
given a label P or N
? Sequence of peaks following a stimulus, thought
to reflect the sequence of neural and cognitive
processes triggered by onset of that stimulus
16
Electrophysiological StudiesERPs

• Advantages
• High temporal resolution (millisecond)
• Makes it great for studying Attention because can
  provide a precise index of timing of attentional
  processes
• Continuous measure
• Provides a continuous measure of processing
  between stimulus and response
• Disadvantages
• Poor spatial resolution
• Can be difficult to localize where in the brain a
  source is coming from
• Most ERP components are quite small
• Need a very large of trials

17
Methods of Cognitive Neuroscience

• ? Patient Studies
  ? Electrophysiological Studies ?
  Neuroimaging Studies

18
Neuroimaging StudiesFunctional Magnetic
Resonance Imaging (fMRI)
Study of Blood Flow Thought ? Increased Neural
Activity ? Increased Blood Flow ? Measure This
Increase in Blood Flow
19
Neuroimaging StudiesFunctional Magnetic
Resonance Imaging (fMRI)

• Measure of blood flow reflected by
• Blood Oxygenation Level Dependent (BOLD) signal
• Ratio of oxygenated to deoxygenated blood
• Magnetic detectors measure changes in this ratio
• An indirect measure of neural activity, but
  findings suggest the BOLD signal accurately
  reflects ongoing neural activity

20
Neuroimaging StudiesfMRI
Memory Encoding vs. Memory Retrieval
Wagner et al. (1998) Remembering and forgetting
of verbal experiences as predicted by brain
activity
Does neural activation differ for subsequently
remembered and subsequently forgotten words?

• Brain activation measured with fMRI during
  encoding of words

?Participants later given a recognition memory
test
21
Neuroimaging StudiesfMRI
Wagner et al. (1998) Remembering and forgetting
of verbal experiences as predicted by brain
activity

• Used an event-related design
• ability to analyze single trials

• Found greater activity in left prefrontal and
  temporal cortices (hippocampal areas) for later
  remembered words in comparison to those forgotten

• Provides support for the encoding-failure
  hypothesis

22
Theory of Mind (ToM)

• Theory of Mind (ToM) our ability to attribute
  mental states, such as beliefs and desires, to
  other social agents and in doing so predict and
  explain their behavior
• Predominantly studied from a developmental
  perspective, through the use of behavioral
  studies
• Cognitive Neuroscience approach
• fMRI
• What areas of the brain are specifically involved
  in calculating the mental states of others?
• Goal uncover areas of the brain specifically
  involved in this process

23
Theory of Mind (ToM)

• fMRI Study ToM Task
• Participants were scanned while watched short
  clips (5 seconds) of people performing either
  real actions or pretend actions
• What areas of the brain are activated when
  participants have to make mental state
  interpretations (pretend conditions)?

Real Action
Pretend Action
German, Niehaus, Roarty, Giesbrecht, Miller
(2004)
24
Theory of Mind Areas

• Pretend Actions vs. Real Actions

• MPFC, Medial Temporal Lobe, Temporo-
• Parietal Junction

25
Neuroimaging Studies

• Advantages
• Neural activity in normal brain
• Localize specific cognitive processes
• High spatial resolution
• Disadvantages
• Indirect measure of neural activity
• Poor temporal resolution (2 seconds)
• Measures slow changes in blood flow

26
Methods of Cognitive Neuroscience

• Patient Studies
  ? Electrophysiological Studies ?
  Neuroimaging Studies
• ? Converging these methods is a key in the study
  of Cognitive Neuroscience