Plasticity

Question 1

Multisensory Integrated - basics

Answer 1

Multisensory interactions can be found in the association areas of the cortex

• e.g. both the secondary visual and auditory cortex feed into the multisensory regions of the parietal and frontal cortex

BUT actually not that simple

• evidence to show that sensory integration already occurs in primary cortices
• these cortices are primarily unisensory but can also share information
• in addition to interactions at primary and secondary levels, the multisensory regions also send information back to primary and secondary cortices

Example: King 2008—> showed that providing a light stimulus in addition to auditory stimulus improved the spatial tuning of responses to sounds in auditory cortex

Question 2

Developmentally Critical Periods of Plasticity

Answer 2

—> developmental critical periods are best for plasticity

example: cat study
- if one eye is shut from birth to 6 months, then opened, barely any neurons in the V1 will respond to the deprived eye. Those that do have abnormal responses
- in contrast those who had both eyes closed as well as the controls showed cell responses for both eyes

—> if eyes were shut for up to 1 year in an adult cat, they do not show different responses to the control

—> visual deprivation must occur in first 3 months in order for the neurons to adapt

Question 3

Long term effects of plasticity in sensory systems

Answer 3

Amputation

• Pioneered by Merzenich 1984:
• after amputating middle finger of monkeys: reorganization of somatosensory cortex

—> other fingers take up the space previously responsible for the middle finger

• important: possible throughout lifespan

Learning

• everyday perceptual learning can also alter sensory representations

—> learning that a combination of stimuli leads to a certain outcome

• new research out of Kerry’s lab:
• mice learned that responding to a specific combination of sound and vibration pattern results in a reward (go/no-go task)
• before training: neurons in barrel cortex did not respond to auditory information or multisensory information (somatosensory cortex)
• after training: neurons improved in tactile responses but also now respond to just auditory discrimination and multisensory information

Question 4

Short-term attention effects

Answer 4

Fritz et al 2003: rapid and reversible plasticity can result from attention or from environmental changes in stimulus
- ferrets learn that during sound type A they can drink normally but sound type B is a warning an electric current will be applied to drinking bottle
- showed that frequency of neurons quickly changes to adapt to attending to specific target frequencies —> greater response for warning sound during task
BUT within seconds of the task finishing, the frequency tuning of the neurons go back to its normal receptive field
—> overall: receptive fields can be tuned to a specific voice in order to block others out and once this voice is no longer present, the receptive field changes again