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Post-activation potentiation in the neocortex: I. Acute preparations
R J Racine1, D Wilson, G C Teskey
1Department of Psychology, McMaster University, Hamilton, Ont., Canada.
Brain Research
|February 21, 1994
Summary
Long-term potentiation (LTP) is reliably expressed in adult rat neocortex without drugs. This memory model shows significant effects in both ipsilateral and contralateral neocortical sites, lasting over two hours.
Area of Science:
- Neuroscience
- Cognitive Science
- Memory Research
Background:
- Long-term potentiation (LTP) is a key cellular mechanism for memory formation.
- Previous studies demonstrated LTP mainly in subcortical areas or required drug intervention in the neocortex.
- Reliable expression of LTP in the neocortex, especially without pharmacological assistance, remains a challenge.
Purpose of the Study:
- To demonstrate reliable expression of LTP in multiple neocortical sites in adult rats without drug-induced attenuation of inhibition.
- To investigate the characteristics of LTP, including its distribution across cortical depths and hemispheres.
- To analyze associated synaptic plasticity phenomena like paired-pulse inhibition and short-term potentiation during LTP induction.
Main Methods:
- Electrophysiological recordings of field potentials in adult rats.
- Stimulation of callosal pathways to induce LTP in ipsilateral and contralateral neocortical sites.
- Monitoring of input/output functions, paired-pulse ratios, and short-term potentiation.
- Assessment of LTP duration over a two-hour period.
Main Results:
- LTP was reliably expressed in various neocortical sites, both ipsilateral and contralateral to stimulation.
- LTP expression was consistent across different cortical depths when recording field potentials.
- Contralateral responses exhibited larger LTP effects, while ipsilateral responses showed shorter latencies and larger amplitudes.
- Paired-pulse depression was observed, and short-term potentiation followed a biexponential decay.
- The induced LTP persisted for at least two hours.
Conclusions:
- Neocortical LTP can be reliably induced and expressed in adult rats without pharmacological manipulation.
- LTP in the neocortex exhibits distinct characteristics in ipsilateral versus contralateral pathways.
- The findings provide a more robust model for studying the cellular basis of memory in the neocortex.