Event-related potentials evoked by passive visuospatial perception in rats and humans reveal common denominators in information processing.

In the human cortex, event-related potentials (ERPs) are triggered in response to sensory, cognitive or motor stimuli. Due to the inherent difficulties of conducting invasive mechanistic studies in human subjects, little is known as to the precise neurophysiological mechanisms that lead to their manifestation. By contrast, although much is known about synaptic and neural mechanisms that underlie information processing in rodents, very few studies have addressed to what extent ERPs are comparable in rodents and humans. Here, we explored this by triggering ERPs in both species during the passive observation of visuospatial imagery, shown in an oddball-like manner, using an experimental design that was equivalent. Several ERP-components were identified in the rodent cohort, corresponding, for example, to the human P1, N1, and P2. ERPs that are likely to reflect a rodent N2 and P300 were also detected. Deviance, as well as repetition effects were evident in both species, whereby rodent ERPs displayed more immediate response alterations to repeated stimuli and humans showed more gradual response shifts. These results indicate that humans and rodents may implement similar strategies for the passive perception and initial processing of visuospatial imagery, despite clear differences in their sensory and cognitive capacities.

Role of the group III metabotropic glutamate receptor in LTP, depotentiation and LTD in dentate gyrus of freely moving rats.

We investigated whether group III metabotropic glutamate (mGlu) receptors are critically involved in the expression of long-term potentiation (LTP), depotentiation, or long-term depression (LTD) in the dentate gyrus of freely moving rats. Male Wistar rats (7 8 weeks) underwent implantation of stimulating and recording electrodes in the medial perforant path and dentate gyrus granule cell layer, respectively. A cannula was permanently implanted into the ipsilateral cerebral ventricle to enable drug administration. Intracerebral injection of the group III mGlu receptor agonist, L(+)-2-amino-4-phosphonobutanoic acid (AP4), significantly inhibited LTP at a concentration which unaffects basal synaptic transmission. Depotentiation. short-term depression (STD) and LTDwere unaffected by the agonist. The antagonist. (R.S)-r-cyclopropyl-4-phosphonophenylglycine (CPPG), inhibited agonist effects. but had no independent effects on basal synaptic transmission. CPPG did not affect the profile of LTP, depotentiation or STD elicited by low frequency stimulation (LFS) at 0.5 or 3 Hz. but significantly impaired LTD expression (at I Hz) and STD elicited at 5 Hz. These findings suggest that activation of group III mGlu receptors is critically required for LTD. but not LTP or depotentiation in the dentate gyrus and provide evidence for the involvement of separate mechanisms underlying LTD and depotentiation.