Prefrontal Cortex of the Mouse Defined as Cortical Projection Area of the Thalamic Mediodorsal Nucleus

Abstract

In the mouse small amounts of horseradish peroxidase were injected iontophoretically into different portions of the frontal lobe. Out of a large number of mice, 18 with typical injections which together covered most of the anterior half of the cortex were selected, and their retrogradely labeled thalamic cells were described and illustrated in detail. Special emphasis was laid on the cortical projections of the mediodorsal nucleus which were considered to define locus and extent of the prefrontal cortex. The results reveal that topographically the extent of the mouse's prefrontal cortex closely resembles that of the rat, another species of the rodent order. It includes a small area within and dorsal to the rhinal sulcus and a comparatively larger region within the medial half of the anterior cortex. Furthermore, the dorsal tip of the frontal pole is reached by a considerable number of afferents from the mediodorsal nucleus. Whether this last projection also exists in the rat is still disputed. As in the rat, only the sulcal prefrontal cortex seems to be reached by mediodorsal cells alone, whereas the rest of the prefrontal cortical fields have overlapping projections from the anteromedial nucleus. Though a considerable area within the frontal lobe of the mouse is reached by mediodorsal afferents, the significance and usefulness of this definition of the prefrontal cortex is questioned.

Cytoarchitectonic and chemoarchitectonic characterization of the prefrontal cortical areas in the mouse

“…To date, little is known about such connectivity patterns in the mouse brain. Only one mouse study was published 29 years ago on the connections of the medial and lateral prefrontal cortex with the mediodorsal nucleus of the thalamus (Guldin et al 1981). This study demonstrates that the medial and lateral ‘PFC’ areas receive mediodorsal connections.…”

Pyramidal Neurons Are Not Generalizable Building Blocks of Cortical Networks

“…The mouse cortical area that is arguably the closest anatomical analog is the dorsomedial frontal cortex (including area FR2) which receives dense inputs from the mediodorsal nucleus of the thalamus (Guldin et al, 1981; Van De Werd et al, 2010) just as the LPFC of the primate does. In marked contrast to the significant differences in L3 pyramidal neurons observed between these two areas in the rhesus monkey, L3 pyramidal neurons in the mouse V1 and FC (FR2) exhibit very modest differences in dendritic structural properties -V1 neurons being slightly smaller than FC- and are nearly identical with regard to physiological features assessed in vitro (Table 1).…”

Reciprocal Connections between Medial Prefrontal Cortex and Lateral Posterior Nucleus in Rats

“…Donoghue and Wise's [1982] cytoarchitectonie classification will be employed for the frontal cortex, Bold et al's [1984] and Paxinos and Watson's [1986] atlas for the dorsal thalamus, and Takahashi's [1985] description for LP. As a control for spread of label into area 24 just medial to AGm, and the lateral agranular field (primary motor cortex for rats) just lateral to AGm, the results from the studies of Beckstead [1976Beckstead [ , 1979, Guldin et al [1981], Donoghue and Parham [1983] and Sharp and Gonzalez [1986] on projections to or from those areas were used.…”