Thalamic units firing upon refixation may be responsible for plasticity in visual cortex

Area of Science:

• Neuroscience
• Visual Neuroscience
• Thalamic Function

Background:

• Mature receptive field properties in cortical visual neurons are essential for visual processing.
• The development of these properties is thought to depend on extraretinal signals.
• Previous theories postulated the existence of such signals but lacked direct evidence.

Purpose of the Study:

• To identify the source of the extraretinal signal responsible for visual receptive field development.
• To investigate the role of specific thalamic units in providing this signal.
• To explore the potential of manipulating this signal to influence visual plasticity.

Main Methods:

• Recording neuronal activity in the thalamic internal medullary lamina of alert cats and monkeys.
• Observing unit activity in relation to eye position and saccades.
• Performing thalamic lesions and electrical stimulation to assess effects on visual cortical plasticity in kittens.

Main Results:

• A specific type of thalamic unit was identified that is silent during saccades but active when the eyes are stationary.
• Abolishing the discharge of these thalamic units via lesioning prevented plastic changes in the visual cortex.
• Eliciting the discharge of these units through electrical stimulation facilitated plastic changes in the visual cortex.

Conclusions:

• Thalamic units in the internal medullary lamina provide the extraretinal signal necessary for the development of mature receptive field properties.
• This thalamic signal plays a critical role in visual cortical plasticity.
• Targeting these thalamic units offers a potential mechanism for modulating visual development and recovery.