NMDA lesions in the medial prefrontal cortex impair the ability to inhibit responses during reversal of a simple spatial discrimination

Rodrigo F. Salazar, Wesley White, Laurent Lacroix, Joram Feldon, Ilsun M. White*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Although lesion studies suggest that the rat medial prefrontal cortex (mPFc) is involved in the process necessary for reversal of a particular set of contingencies, the nature of lesion-induced deficits is unclear. The involvement of rat mPFc in reversal of a simple spatial discrimination was examined in the present study. Our hypothesis was that lesion-induced deficits may reflect a failure to inhibit a learned instrumental response. Lister Hooded rats were trained on a spatial discrimination task (SD), which required a correct barpress matching the cue location, then they were trained on reversal of SD (SDR), which required a correct barpress opposite to the cue location. Rats with mPFc lesions showed a slower learning rate compared to the controls. However, behavior of the lesioned rats during early and later reversal differed. During the initial SDR, the lesioned rats showed a greater number of barpresses during the intertrial interval and a slightly higher percent correct responses than that of the controls. Our data suggest that damage to mPFc may produce a lack of response inhibition, leading to an increase in nondiscriminated bapresses, thereby yielding a 'facilitation' during early reversal. mPFc lesion did not affect either open field activity or prepulse inhibition (PPI), a frequently used measure of sensorimotor gating. Disruption of reversal learning following damage to mPFc is partly due to a failure to inhibit instrumental responses, rather than to disruption of other processes involved in sensorimotor gating or general activity.

Original languageEnglish
Pages (from-to)413-424
Number of pages12
JournalBehavioural Brain Research
Issue number2
StatePublished - 9 Jul 2004
Externally publishedYes


FundersFunder number
National Institutes of Health
National Institute of Mental HealthR15MH067606
Eidgenössische Technische Hochschule ZürichTH-32/99-3


    • Openfield activity
    • Prepulse inhibition
    • Response inhibition
    • Spatial learning


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