Representation of three‐dimensional objects by the rat perirhinal cortex

Abstract

The perirhinal cortex (PRC) is known to play an important role in object recognition. Little is known, however, regarding the activity of PRC neurons during the presentation of stimuli that are commonly used for recognition memory tasks in rodents, that is, 3-dimensional objects. Rats in the present study were exposed to 3-dimensional objects while they traversed a circular track for food reward. Under some behavioral conditions the track contained novel objects, familiar objects, or no objects. Approximately 38% of PRC neurons demonstrated ‘object fields’ (a selective increase in firing at the location of one or more objects). Although the rats spent more time exploring the objects when they were novel compared to familiar, indicating successful recognition memory, the proportion of object fields and the firing rates of PRC neurons were not affected by the rats’ previous experience with the objects. Together these data indicate that the activity of PRC cells is powerfully affected by the presence of objects while animals navigate through an environment, but under these conditions, the firing patterns are not altered by the relative novelty of objects during successful object recognition.

D1 and D5 dopamine receptors participate on the consolidation of two different memories

“…Hippocampal lesions [60] and inhibition of hippocampal protein synthesis [55] hinders object recognition memory formation. However, like most other forms of learning [3], object recognition does not depend exclusively on a single region but requires the concourse of others, like the perirhinal cortex [61][62][63]. Some modulatory systems regulate synaptic plasticity and memory formation, among these, the dopaminergic system, which has an important function, especially in the CA1 region of the hippocampus [9][10][11][12][13][14].…”

Medial prefrontal-perirhinal cortical communication is necessary for flexible response selection

“…In fact, lesions to the PER cause impairments in object recognition, but not in spatial memory (Bussey, Muir, and Aggleton, 1999), and lesion data indicate the PER contributes to both object perception and memory (Buckley and Gaffan, 1998b; Murray and Bussey, 1999). Furthermore, a portion of PER neurons are selectively activated by different objects (Burke, Maurer, Hartzell, Nematollahi, Uprety, Wallace, et al, 2012b; Deshmukh, Johnson, and Knierim, 2012), even when the environment in which they are presented is changed (Burke et al, 2012a). Although it is clear that the PER encodes object information, it is unlikely its contribution to the OPPA task is limited to object representations.…”

“…A similar situation may occur when an object is associated with a place. While PER cells do not show spatial selectivity (Burke et al, 2012b; Burwell, Shapiro, O’Malley, and Eichenbaum, 1998), plasticity within PER may bias the retrieval of one object representation over another when the animal is in a specific location and this interaction could be modulated by projections from the mPFC (Paz et al, 2007). A critical issue not addressed by the current study is the necessity of mPFC-PER connectivity to acquire new object-place associations.…”

Spatial and Nonspatial Representations in the Lateral Entorhinal Cortex

“…Correlated with theta modulation of MEC neurons, MEC also has high firing rate (>10 Hz), narrow spike width interneurons (Frank et al 2001;Hargreaves et al 2005;. In contrast, LEC lacks theta modulation (Deshmukh et al 2010), and correspondingly, LEC and PRC do not show high firing rate interneurons during foraging ; but see Burke et al 2012). This absence of high firing rate interneurons in the PRC-LEC pathway indicates that fundamentally different network level computations are involved in information processing in PRC and LEC, compared to those involved in path integration computations in MEC and hippocampus.…”