Related Experiment Videos
Postnatal development of functional properties of visual cortical cells in rats with excitotoxic lesions of basal
R Siciliano1, G Fontanesi, F Casamenti
1Department of Physiology and Biochemistry, University of Pisa, Italy.
Insights
Cholinergic input from the basal forebrain (BF) influences visual cortex development. Disrupting this input transiently alters ocular dominance in rats during the critical period but has no lasting effects.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Visual System Development
Background:
- Visual cortical cells mature during a critical period (postnatal days 15-40).
- Cholinergic afferents from the basal forebrain (BF) are crucial for this development.
Purpose of the Study:
- To investigate the influence of BF cholinergic input on visual cortical neuron development.
- To assess functional properties like ocular dominance and orientation selectivity.
Main Methods:
- Unilateral BF cholinergic lesions were induced in rats at postnatal day 15.
- Extracellular recordings assessed visual cortical cell properties during and after the critical period.
- Cholinergic depletion was verified post-mortem.
Main Results:
- BF cholinergic lesions transiently altered ocular dominance, with more cells driven by the contralateral eye during the critical period.
- Other functional properties (orientation selectivity, receptive-field size, cell responsiveness) remained unaffected.
- Ocular dominance normalized after the critical period ended.
Conclusions:
- BF cholinergic neurons transiently impact cortical competitive processes during development.
- The effects of cholinergic deafferentation are temporary and resolve after the critical period.
Abstract:
In the rat, visual cortical cells develop their functional properties during a period termed as critical period, which is included between eye opening, i.e. postnatal day (PD) 15, and PD40. The present investigation was aimed at studying the influence of cortical cholinergic afferents from the basal forebrain (BF) on the development of functional properties of visual cortical neurons. At PD15, rats were unilaterally deprived of the cholinergic input to the visual cortex by stereotaxic injections of quisqualic acid in BF cholinergic nuclei projecting to the visual cortex. Cortical cell functional properties, such as ocular dominance, orientation selectivity, receptive-field size, and cell responsiveness were then assessed by extracellular recordings in the visual cortex ipsilateral to the lesioned BF both during the critical period (PD30) and after its end (PD45). After the recording session, the rats were sacrificed and the extent of both cholinergic lesion in BF and cholinergic depletion in the visual cortex was determined. Our results show that lesion of BF cholinergic nuclei transiently alters the ocular dominance of visual cortical cells while it does not affect the other functional properties tested. In particular, in lesioned animals recorded during the critical period, a higher percentage of visual cortical cells was driven by the contralateral eye with respect to normal animals. After the end of the critical period, the ocular dominance distribution of animals with cholinergic deafferentation was not significantly different from that of controls. Our results suggest the possibility that lesions of BF cholinergic neurons performed during postnatal development only transiently interfere with cortical competitive processes.