Memory fields of neurons in the primate prefrontal cortex

Abstract

Many prefrontal (PF) neurons convey information about both an object's identity (what) and its location (where). To explore how they represent conjunctions of what and where, we explored the receptive fields of their mnemonic activity (i.e., their ''memory fields'') by requiring monkeys to remember both an object and its location at many positions throughout a wide portion of central vision. Many PF neurons conveyed object information and had highly localized memory fields that emphasized the contralateral, but not necessarily foveal, visual field. These results indicate that PF neurons can simultaneously convey precise location and object information and thus may play a role in constructing a unified representation of a visual scene.

Spatial maps in frontal and prefrontal cortex

“…Although there is strong evidence of this area's involvement in working memory tasks (Goldman-Rakic, 1987;Funahashi et al, 1989;Owen et al, 1996;Braver et al, 1997;Rainer et al, 1998), some have suggested that the basic role of DLPFC is to maintain an abstract representation of the rules of a task (Miller et al, 2002;Derrfuss et al, 2004) and to select responses (Rowe et al, 2000). Our results suggest some degree of functional subdivision within DLPFC as the maps do not completely cover the posterior DLPFC region activated by our task (Figs.…”

“…There are several reasons why maps in higherlevel areas are more difficult to accurately and reliably measure. First, in areas such as DLPFC, only a subset of neurons display spatial preference (Funahashi et al, 1989;Rainer et al, 1998). Second, task-related activity that is non-spatially selective could cause fluctuations in blood oxygenation level dependent (BOLD) signals that actively reduce the significance of the correlation with stimulus location; this effect could differ between hemispheres.…”

“…It has been argued that the human homologues of both the FEF and the principal sulcus area are located more superiorly than in monkeys (Courtney et al, 1998), suggesting that our DLPFC focus may be comparable to a more region inferior to the FEF and the principal sulcus in monkeys. The task we used to identify these new maps in human prefrontal cortex is more complicated in terms of mental components required than the simple spatial working memory tasks often used in monkey working memory studies; however, the 2-back task is essentially a continuously running version of the object-based match-to-sample task, which has been used successfully in monkeys (Rainer et al, 1998). In that study, prefrontal neurons -particularly those inferior to the principal sulcus -were found to display ''memory fields''; that is, task-related activity with spatial preference.…”

“…Physiological recordings in monkeys have demonstrated that prefrontal areas have spatially selective memory fields that primarily represent restricted regions of contralateral space (Funahashi et al, 1989;Rainer et al, 1998). It seems plausible that maps of visual space might be preserved, rather than scrambled, as posterior visual areas project to frontal and prefrontal cortex.…”

Cortical correlates of learning in monkeys adapting to a new dynamical environment

“…At the cellular level, learning-dependent neuronal activity has been found in the premotor cortex (16), the supplementary motor cortex (17,18), the supplementary eye field (19), the prefrontal cortex (20,21), and the somatosensory areas (22). With respect to the primary motor cortex, the study of Wise et al (23) also has shown learning at the level of the cells of this area.…”