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Experiment Overview

• Classic experiment by David Hubel and Torsten Wiesel.
• Focus on recording the receptive field of a single neuron in the primary visual cortex (V1) of an anesthetized cat using a microelectrode.
• Method:
  • A microelectrode is implanted in V1.
  • A bar of light is shined on various locations in the cat's visual field.
  • The microelectrode is connected to a speaker that registers each action potential as a clicking signal.

Neuronal Response

• The neuron exhibits vigorous firing to a bar of light at approximately 45 degrees.
• Firing patterns of the neuron are recorded by marking locations with Xs.

ON Receptive Field

• Response to light:
  • The neuron primarily responds to the onset of light in its ON receptive field.
  • The ON receptive field is marked by Xs.
  • The neuron also reacts to changes of light in parallel areas on either side of the Xs.

OFF Fields

• OFF fields are recorded as triangles.
• Neuronal activity:
  • More activity is observed in the OFF field below the axis (5 triangles) than above it (3 triangles).

Receptive Field Characteristics

• Each neuron has its unique preferred orientation and receptive field region.
• The on-center region is indicated by a solid axis and represents where the maximum firing occurs when light is presented at the preferred orientation.
• Simple cells are characterized as cells in the primary visual cortex with specific receptive fields that display orientation preferences.
• Widening the bar of light reduces the firing rate of the cell.