Biology subjects

Inostroza, M.

Publications and source records attributed to Inostroza, M..

4 recordsLinked to original sources

bioRxiv2026

Hunger and sleep recruit distinct brain systems to form spatial memory

By demonstrating that hunger consolidates spatial memory via a non-hippocampal mechanism that critically involves the retrosplenial cortex, we identify a mode of memory formation that is distinct from well-known hippocampus-dependent memory formation during sleep. Food-deprived rats encoded object locations and, during a subsequent 2-h consolidation phase, either received food and slept (Sleep-Fed) or stayed awake (Wake-Fed), or remained hungry and stayed awake (Wake-Hungry). At later retrieval testing, both Wake-Hungry and Sleep-Fed rats exhibited robust spatial memory, whereas Wake-Fed rats did not. Blocking neuropeptide-Y (NPY) signaling during the consolidation phase abolished hunger-consolidated memory. Unlike sleep-dependent consolidation, hunger-consolidated memory did not require the hippocampus during consolidation or retrieval, and not even during encoding. In contrast, inhibiting retrosplenial cortex during retrieval abolished hunger-consolidated memory but spared memory formed during sleep. Thus, recruitment of brain systems to form spatial memory is tuned to specific brain states, and fundamentally differs between sleep and hunger.

neuroscience↗

bioRxiv2026

Juvenile rat's sleep enables schema memory across episodes before expression of memory for individual episodes

Schema memory refers to generalized knowledge extracted from multiple related episodes. According to systems consolidation theory, such representations emerge during sleep through the transformation of hippocampus-dependent episodic memories into neocortical schema representations. Whether this process requires mature episodic memory expression during early development remains unclear. Here, we examined schema formation in infant rats with an immature hippocampus. At postnatal day (PD) 25, pups (n=24) were tested in an adapted object-place paradigm enabling abstraction of a spatial regularity across eight consecutive episodes. Following encoding, pups either slept or remained awake for two hours, and schema memory was tested 22 hours later. Control groups were exposed to pseudorandomized object configurations. Schema memory was expressed only after exposure to spatial regularities and only when sleep followed encoding. To directly assess episodic memory under comparable conditions, an additional group of pups (n=12) was tested in a standard single-episode object-place recognition (OPR) task with post-encoding sleep. At a 4-hours test, these pups did not show episodic object-place memory. These findings indicate that sleep supports schema memory formation during early life under conditions in which the expression of robust single-episode memory is not yet evident, suggesting that schema abstraction in infancy does not depend on fully developed hippocampal episodic representations.

neuroscience↗

bioRxiv2026

Hippocampus consolidates memory in the upstate of cortical sleep slow oscillations

Cortical slow oscillations (SOs), a hallmark of non-rapid eye movement (NonREM) sleep, have been proposed to support systems memory consolidation by organizing hippocampal-cortical communication. However, whether consolidation requires hippocampal memory processing during SO-defined windows is unclear. Here, we used closed-loop optogenetics to transiently inhibit dorsal hippocampal activity in adult rats (N = 12) during NonREM sleep following object-place association learning, either during cortical SO upstates or outside SOs, compared with a no-stimulation control. Inhibition during SO upstates completely abolished expression of memory at retrieval, despite preserved sleep architecture and intact cortical SO and spindle dynamics. By contrast, inhibition outside SOs preserved memory and only slightly reduced performance compared to the no-stimulation control. Memory impairment from hippocampal inhibition was largely mediated by SO upstates nesting spindles. Our findings provide novel evidence that sleep-dependent systems consolidation requires precisely timed hippocampal-neocortical dialogue.

neuroscience↗

bioRxiv2022

An evolutionary conserved division-of-laborbetween hippocampal and neocortical sharp-wave ripplesorganizes information transfer during sleep

The hippocampal sharp-wave ripple (SW-R) is the key substrate of the hippocampal-neocortical dialogue underlying memory formation. Recently, it became evident that SW-R are not unique to archicortex, but constitute a wide-spread neocortical phenomenon. To date, little is known about morphological and functional similarities between archi- and neocortical SW-R. Leveraging intracranial recordings from the human hippocampus and prefrontal cortex during sleep, our results reveal region-specific functional specializations, albeit a near-uniform morphology. While hippocampal SW-R trigger directional hippocampal-to-neocortical information flow, neocortical SW-R reduce information flow to minimize interference. At the population level, hippocampal SW-R confined population dynamics to a low-dimensional subspace, while neocortical SW-R diversified the population response; functionally uncoupling the hippocampal-neocortical network. Critically, our replication in rodents demonstrated the same division-of-labor between archi-and neocortical SW-R. These results uncover an evolutionary preserved mechanism where coordinated interplay between hippocampal and neocortical SW-R temporally segregates hippocampal information transfer from neocortical processing.

neuroscience↗