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Alterations in visual receptive fields in the superior colliculus induced by amphetamine
K L Grasse1, R M Douglas, J R Mendelson
1Department of Psychology, York University, Ontario, Canada.
Experimental Brain Research
|January 1, 1993
Summary
d-amphetamine significantly expands visual receptive fields (RFs) in the superior colliculus (SC) of cats, suggesting local inhibitory networks modulate visual processing. This drug temporarily increases the effective retinal area influencing SC activity.
Area of Science:
- Neuroscience
- Visual processing
- Pharmacology
Background:
- The superior colliculus (SC) plays a crucial role in visual information processing.
- Understanding the mechanisms that shape receptive fields (RFs) in the SC is essential for comprehending visual perception.
- The influence of neuromodulators on SC visual function remains an area of active investigation.
Purpose of the Study:
- To investigate the effects of d-amphetamine on visual response properties in the superficial layers of the cat's SC.
- To determine if d-amphetamine alters receptive field size and surround suppression in the SC.
- To explore the origin of drug-induced RF changes, differentiating between retinal, cortical, and SC-intrinsic mechanisms.
Main Methods:
- Electrophysiological recordings were performed on anesthetized, paralyzed cats.
- Single unit receptive fields in the SC superficial layers were mapped before and after intravenous d-amphetamine administration.
- Stimuli included small light spots, light bars of varying lengths, and flashed stimuli at different locations.
Main Results:
- Intravenous d-amphetamine caused a significant, temporary expansion of SC receptive field size, averaging a 5.6-fold increase.
- RF expansion was predominantly horizontal and diminished surround suppression, particularly for stimuli exceeding the control RF diameter.
- No significant changes in RF size were observed after intravitreal d-amphetamine or in the visual cortex, indicating a non-retinal and non-cortical origin for the SC effects.
Conclusions:
- D-amphetamine administration dynamically modulates visual receptive fields in the superior colliculus.
- The findings suggest that local inhibitory networks within the SC may shape RFs and are sensitive to amphetamine-induced modulation.
- The effective retinal area influencing SC activity may be considerably larger than conventionally estimated, highlighting the dynamic nature of visual processing in the SC.