Different Contributions of the Hippocampus and Perirhinal Cortex to Recognition Memory

Abstract

Brain regions involved in visual recognition memory, including the hippocampus, have been investigated by measuring differential neuronal activation produced by novel and familiar pictures. Novel and familiar pictures were presented simultaneously, one to each eye, using a paired viewing procedure. Differential neuronal activation was determined using immunohistochemistry for the protein products of c-fos as an imaging technique. The results establish that the regions of the rat brain associated with discriminating the novelty or familiarity of an individual item (such as a single object) differ from those responding to a spatial array of items (such as a scene). Perirhinal cortex and area TE of the temporal lobe are activated significantly more by pictures of novel than of familiar individual objects, but the hippocampus is not differentially activated. In contrast, pictures of novel arrangements of familiar items produce significantly greater activation than familiar arrangements of these items in postrhinal cortex and subfield CA1 of the hippocampus but significantly less activation in the dentate gyrus and subiculum; perirhinal cortex and area TE are not differentially activated. Thus, the hippocampus is importantly involved in processing information essential to recognition memory concerning the relative familiarity of arrangements of items, as needed for episodic memory of scenes, whereas the perirhinal cortex processes such information for individual items.

Regional activation of the human medial temporal lobe during intentional encoding of objects and positions

“…Here, we found that the perirhinal cortex was bilaterally more engaged by object encoding compared to position encoding. This supports our hypothesis that the perirhinal cortex is involved in object-specific encoding; and the finding corroborates similar results from both the human and non-human primate literature (Aggleton and Brown, 2005;Wan et al, 1999;Bussey et al, 2002Bussey et al, , 2005. Converging evidence from lesion studies of monkeys (Baxter and Murray, 2001), rats (Prusky et al, 2004) and humans (Barense et al, 2005), as well as from neuroimaging studies (Pihlajamäki et al, 2005) have implicated the perirhinal cortex in object processing.…”

The rat perirhinal cortex: A review of anatomy, physiology, plasticity, and function

“…Lesions of the perirhinal cortex result in impairments in recognition but not spatial tasks whereas lesions of the hippocampus result in impairments in spatial but recognition tasks (Ennaceur and Aggleton, 1994;Bussey et al, 2000;Abe et al, 2009). Similarly, electrophysiological (Zhu and Brown, 1995;Zhu et al, 1995a) and c-Fos studies (Zhu et al, 1996(Zhu et al, , 1997Wan et al, 1999;Jenkins et al, 2004;Amin et al, 2006) have shown that the perirhinal cortex is recruited more during recognition than spatial tasks and vice versa for the hippocampus. There is mounting evidence to suggest that the hippocampus may indeed play a role in recognition memory (Hammond et al, 2004;Prusky et al, 2004) but the overwhelming consensus is that the perirhinal cortex alone is sufficient for completing recognition memory tasks.…”

“…Immediate early gene imaging studies have shown that the perirhinal cortex is activated following object recognition tasks (Wan et al, 1999;Aggleton and Brown, 2005;Warburton et al, 2005) and following the presentation of novel visual stimuli (Zhu et al, 1995b(Zhu et al, , 1996(Zhu et al, , 1997, thus indicating that the perirhinal cortex plays a central role in novelty detection. Lesions of the perirhinal cortex have been shown to impair performance in the object recognition task (Ennaceur et al, 1996;) and more recent work has shown that the perirhinal cortex is required for the encoding, consolidation and retrieval of object recognition memory (Winters and Bussey, 2005a,b;Winters et al, 2008).…”

“…Recently, exercise-induced enhancement in performance in a novel object recognition task has been associated with concurrent increases in perirhinal BDNF expression in the rat (Hopkins and Bucci, 2010) and interference of perirhinal BDNF signalling has been shown to disrupt long-term recognition memory (Seoane et al, 2011). Immediate early gene imaging studies also show that perirhinal cortex is recruited during recognition tasks; there is increased c-Fos expression in the perirhinal cortex following exposure to novel visual stimuli (Zhu et al, 1995b(Zhu et al, , 1997Wan et al, 1999) but not after exposure to familiar visual stimuli (Zhu et al, 1996).…”

A Role of Fos Expression in the CA3 Region of the Hippocampus in Spatial Memory Formation in Rats

“…The expression of c-fos is induced by a variety of stimuli (Smith et al 1992;Melia et al 1994;Duncan et al 1996) and after some forms of learning (McCabe and Horn 1994;Radulovic et al 1998;Wan et al 1999;Vann et al 2000). Accordingly, Fos expression is considered a mechanism by which brief stimuli can trigger long-term changes in gene expression and alter the structural and functional properties of nerve cells (Goelet et al 1986;Morgan and Curran 1991).…”