Menno P Witter

Learn More
Grid cells in the medial entorhinal cortex (MEC) are part of an environment-independent spatial coordinate system. To determine how information about location, direction, and distance is integrated in the grid-cell network, we recorded from each principal cell layer of MEC in rats that explored two-dimensional environments. Whereas layer II was predominated(More)
In the early 1970s, Andersen and colleagues proposed that the principal excitatory pathways of the hippocampal formation were organized in a lamellar fashion. This proposition, based heavily on the physiological studies of the proponents, indicated that "a point source of entorhinal activity projects its impulses through the four membered pathway (of the(More)
Place cells in hippocampal area CA1 may receive positional information from the intrahippocampal associative network in area CA3 or directly from the entorhinal cortex. To determine whether direct entorhinal connections support spatial firing and spatial memory, we removed all input from areas CA3 to CA1, thus isolating the CA1 area. Pyramidal cells in the(More)
As the interface between hippocampus and neocortex, the entorhinal cortex is likely to play a pivotal role in memory. To determine how information is represented in this area, we measured spatial modulation of neural activity in layers of medial entorhinal cortex projecting to the hippocampus. Close to the postrhinal-entorhinal border, entorhinal neurons(More)
This review is prompted by recent findings that the perirhinal and parahippocampal cortices in the monkey brain are important components of the medial temporal lobe memory system. Given the potential importance of the comparable rcgions 1 0 niemory function in rhe rat brain, it is surprising that so little is known about their neuroanatomy. In fact, there(More)
Grid cells are topographically organized in the sense that, within the dorsal part of the medial entorhinal cortex, the scale of the grid increases systematically with anatomical distance from the dorsal border of this brain area. The ventral limit of the spatial map is currently not known. To determine if the grid map extends into the intermediate and(More)
The anatomical organization of the parahippocampal-hippocampal network indicates that it consists of different parallel circuits. Considering the topographical distribution of sensory cortical inputs, the hypothesis is that the major parallel circuits carry functionally different information. These functionally different parallel routes reach different(More)
In the adult brain, space and orientation are represented by an elaborate hippocampal-parahippocampal circuit consisting of head-direction cells, place cells, and grid cells. We report that a rudimentary map of space is already present when 2 1/2-week-old rat pups explore an open environment outside the nest for the first time. Head-direction cells in the(More)
The origins and terminations of entorhinal cortical projections in the rat were analyzed in detail with retrograde and anterograde tracing techniques. Retrograde fluorescent tracers were injected in different portions of olfactory, medial frontal (infralimbic and prelimbic areas), lateral frontal (motor area), temporal (auditory), parietal (somatosensory),(More)