Psych202 - Foundations of Cognitive Neuroscience
Lecture 10 - Plasticity
Overview
1. Brain Plasticity in Animals and Humans - how do we observe it and what is it
2. Mechanisms of Plasticity
Section 1 - Brain Plasticity in Animals and Humans
Brain Plasticity
● The brain changes itself through thinking! (also mean perceiving)
● A feature of the brain whereby its structure and function change all the time, through perception,
task performance, and after damage
● One of the biggest discoveries of brain science - Cumulative discovery beginning in the 1960s
● In contrast to previous view: brain is a fixed mechanism (19th century & most of the 20th century –
computer analogy)
Consequences of Plasticity
● Cortical reorganisation: a piece of cortex that loses its function (doesn't lie dormant), and takes up
a new task.
● Cortical expansion: The size of the represented body part in the cortex depends on the amount of
use of that part.
● Memory: Synapses can be strengthened or weakened over various time scales. (Hebb's law - fire
together, wire together)
Plasticity Continues throughout Life
● In infants, plasticity is non-selective, all stimuli induce plastic changes = critical period of
development
● In adult brains, plasticity is selectíve, controlled by task demands and context
● Salient stimuli induce plasticity:
○ Stimuli in the focus of attention (i.e. in working memory)
○ Surprising stimuli
○ Stimuli which are associated with a reward
Seeing through Echolocation
● Neuroplasticity
● Cortical reorganisation
● Tongue clicks - feedback from the environment - visually impaired
Cortical Reorganization: Visual Cortex
● Thaler et al. (2011) fMRI study
● Participants: blind echolocation experts & controls
● Conditions: (1) clicks with echoes; (2) clicks without echoes
● Echolocator: increases in BOLD activity in the primary visual cortex -
more neural activity when the clicks were accompanied by echoes
● Control: No contrasts
● Conclusion: Echolocation recruits the visual cortex for auditory processing
● Note: These results do not indicate that the auditory cortex is inactive! There is merely no contrast
between the conditions.
, Sensory and Motor Models
Posterior to the central sulcus - each part of the body has its own location on the
cortex - Homunculus
Similar homunculus
Cortical expansion in Somatosensory Cortex
● Jenkins et al (1990): microelectrode study in adult monkey
● Repeated stimulation of fingertip (109 days, 1.5 h per day)
● Result: enlarged representation of fingertip in the somatosensory cortex -
cortical expansion
Cortical expansion in motor cortex
● Elbert et al. (1995): MEG study
● Participants: string players & controls
● Somatosensory stimulation: thumb (D1) and little finger (D5) of left and right hand.
● Dependent variable: Distance between areas activated by D1 and D5
Yellow Arrows:
Equivalent current dipoles (ECDs) =
Estimates of the primary currents generating the event-related field - assume they
are point-like and you can solve the reverse problem
String players have a larger representation of the left hand.
Distance between the thumb and the little finger becomes bigger
MMN to Tone Sequence Violation
● MMN caused by a slight change in 8-tone melody presented as standard
● Evidence for temporal binding - melody is represented in the auditory cortex
● Std and Dev melody represented in auditory cortex as distinct
time-extended ”objects”
● MMN reflects perception - due to synapses becoming weaker in the
auditory cortex
Perceptual Learning through Plasticity
● Some participants don’t show MMN at start of experiment
● They can’t hear the difference
● The MMN emerges during the experiment
● The participants start to hear the difference
● Interpretation: plastic changes in auditory cortex leading to perceptual
learning - heard it from the beginning observed a large mismatch response
Lecture 10 - Plasticity
Overview
1. Brain Plasticity in Animals and Humans - how do we observe it and what is it
2. Mechanisms of Plasticity
Section 1 - Brain Plasticity in Animals and Humans
Brain Plasticity
● The brain changes itself through thinking! (also mean perceiving)
● A feature of the brain whereby its structure and function change all the time, through perception,
task performance, and after damage
● One of the biggest discoveries of brain science - Cumulative discovery beginning in the 1960s
● In contrast to previous view: brain is a fixed mechanism (19th century & most of the 20th century –
computer analogy)
Consequences of Plasticity
● Cortical reorganisation: a piece of cortex that loses its function (doesn't lie dormant), and takes up
a new task.
● Cortical expansion: The size of the represented body part in the cortex depends on the amount of
use of that part.
● Memory: Synapses can be strengthened or weakened over various time scales. (Hebb's law - fire
together, wire together)
Plasticity Continues throughout Life
● In infants, plasticity is non-selective, all stimuli induce plastic changes = critical period of
development
● In adult brains, plasticity is selectíve, controlled by task demands and context
● Salient stimuli induce plasticity:
○ Stimuli in the focus of attention (i.e. in working memory)
○ Surprising stimuli
○ Stimuli which are associated with a reward
Seeing through Echolocation
● Neuroplasticity
● Cortical reorganisation
● Tongue clicks - feedback from the environment - visually impaired
Cortical Reorganization: Visual Cortex
● Thaler et al. (2011) fMRI study
● Participants: blind echolocation experts & controls
● Conditions: (1) clicks with echoes; (2) clicks without echoes
● Echolocator: increases in BOLD activity in the primary visual cortex -
more neural activity when the clicks were accompanied by echoes
● Control: No contrasts
● Conclusion: Echolocation recruits the visual cortex for auditory processing
● Note: These results do not indicate that the auditory cortex is inactive! There is merely no contrast
between the conditions.
, Sensory and Motor Models
Posterior to the central sulcus - each part of the body has its own location on the
cortex - Homunculus
Similar homunculus
Cortical expansion in Somatosensory Cortex
● Jenkins et al (1990): microelectrode study in adult monkey
● Repeated stimulation of fingertip (109 days, 1.5 h per day)
● Result: enlarged representation of fingertip in the somatosensory cortex -
cortical expansion
Cortical expansion in motor cortex
● Elbert et al. (1995): MEG study
● Participants: string players & controls
● Somatosensory stimulation: thumb (D1) and little finger (D5) of left and right hand.
● Dependent variable: Distance between areas activated by D1 and D5
Yellow Arrows:
Equivalent current dipoles (ECDs) =
Estimates of the primary currents generating the event-related field - assume they
are point-like and you can solve the reverse problem
String players have a larger representation of the left hand.
Distance between the thumb and the little finger becomes bigger
MMN to Tone Sequence Violation
● MMN caused by a slight change in 8-tone melody presented as standard
● Evidence for temporal binding - melody is represented in the auditory cortex
● Std and Dev melody represented in auditory cortex as distinct
time-extended ”objects”
● MMN reflects perception - due to synapses becoming weaker in the
auditory cortex
Perceptual Learning through Plasticity
● Some participants don’t show MMN at start of experiment
● They can’t hear the difference
● The MMN emerges during the experiment
● The participants start to hear the difference
● Interpretation: plastic changes in auditory cortex leading to perceptual
learning - heard it from the beginning observed a large mismatch response
