introduction: the learning procedure leads to biochemical, biophysical and ultrastructural changes in synapses of some specific areas in central nervous system, which is named synaptic plasticity. material and methods: twelve male wistar rats were divided in two (case and control) groups. the cases were trained in morris water maze. the animals underwent 8 training sessions per day, on 3 consec...

Neuronal firing in the hippocampal formation (HF) of freely moving rodents shows striking examples of spatialorganization in the form of place, directional, boundary vector and grid cells. The firing of place and grid cells shows an intriguing form of temporal organization known as 'theta phase precession'. We review the mechanisms underlying theta phase precession of place cell firing, ranging...

Both field and laboratory studies demonstrate that hummingbirds (Apodiformes, Trochilidae) have exceptional spatial memory. The complexity of spatial-temporal information that hummingbirds must retain and use daily is probably subserved by the hippocampal formation (HF), and therefore, hummingbirds should have a greatly expanded HF. Here, we compare the relative size of the HF in several hummin...

The hippocampal formation (HF) is implicated in a comparator that detects sensory conflict (mismatch) among convergent inputs. This suggests that new place cells encoding the new configuration with sensory mismatch develop after the HF learns to accept the new configuration as a match. To investigate this issue, HF CA1 place cell activity in rats was analyzed after the adaptation of the rats to...

The hippocampal formation (HF) plays a key role in novelty detection, but the mechanisms remain unknown. Novelty detection aids the encoding of new information into memory-a process thought to depend on the HF and to be modulated by the theta rhythm of EEG. We examined EEG recorded in the HF of rats foraging for food within a novel environment, as it became familiar over the next five days, and...

A connectome is an indispensable tool for brain researchers, since it quickly provides comprehensive knowledge of the brain's anatomical connections. Such knowledge lies at the basis of understanding network functions. Our first comprehensive and interactive account of brain connections comprised the rat hippocampal-parahippocampal network. We have now added all anatomical connections with the ...

Two experiments compared the effects of bilateral lesions of the hippocampal formation (HPC) or perirhinal cortex (PRh) on rats' performance of an allocentric spatial working memory task--delayed matching-to-place (DMTP) in a water maze. DMTP trials consisted of paired swims, and the hidden platform was moved to a new location on each trial. Performance was assessed with intervals between the f...

The role of the hippocampal formation (HF) in memory processing was assessed in food-storing black-capped chickadees (Poecile atricapilla) by reversibly inactivating the HF during different memory tests. The memory tests required birds to remember a location based on spatial cues only, or based on a combination of both spatial and distinct visual cues. Inactivation of the HF impaired short-term...

The volume of the hippocampal formation (HF) in black-capped chickadees (Poecile atricapillus) varies across the seasons, in parallel with the seasonal cycle in food hoarding. In this study, we estimate cell density and total cell number in the HF across seasons in both juveniles and adults. We find that the seasonal variation in volume is due to an increase in the number of small and large cel...

The hippocampal formation (HF) of mammals and birds plays a strikingly similar role in the representation of space. This evolutionarily conserved property, however, belies the contrasting spatial ecology of animals such as rats and homing pigeons, differing spatial ecologies that should have promoted the evolution of group-specific adaptations to the HF representation of space. However, the spa...