Biomedical subjects

Janina Ferbinteanu

Publications and source records attributed to Janina Ferbinteanu.

5 recordsLinked to original sources

PubMed2006

Representing episodes in the mammalian brain.

Memory lets the past inform the present so that we can attain future goals. In many species, these abilities require the hippocampus. Recent experiments, in which memory demand was varied while overt behavior and the environment were kept constant, have revealed firing patterns of hippocampal neurons that corresponded with memory demands and predicted performance. Although the active population appeared to be 'place cells' that signalled location, it actually included cells the activity patterns of which distinguished the recent or pending history of behavior during identical actions that occurred in the same place. Different populations of hippocampal cells fired as a rat walked along the same spatial path on the way to different goals, and coded past, present and pending events. Other experiments provide converging data that neuronal activity is modulated by goal-directed behavioral episodes. Together, these firing patterns suggest a testable mechanism of episodic memory coding: that hippocampal dynamics encode a temporally extended, hierarchically organized representation of goal-directed behavior.

Action Potentials↗

PubMed2006

Relative spike timing in pairs of hippocampal neurons distinguishes the beginning and end of journeys.

Episodic memory organizes experience in time, so that we can review past events and anticipate the future. In a hippocampus-dependent memory task, spike timing in pairs of simultaneously active CA1 neurons with overlapping place fields distinguished the start and end of trials. At the common starting point of different journeys, the relative spike timing of the neurons was highly correlated. As the rat approached a common goal from different starting points, however, temporal firing patterns were strongly modulated across journeys even if the cells fired in the same spatial locations within fields, implying that different processes influenced when and where cells fire. Spike timing within hippocampal ensembles may thereby help parse the beginning from the end of episodes in memory.

Action Potentials↗

PubMed2006

Episodic memory--from brain to mind.

Neuronal mechanisms of episodic memory, the conscious recollection of autobiographical events, are largely unknown because electrophysiological studies in humans are conducted only in exceptional circumstances. Unit recording studies in animals are thus crucial for understanding the neurophysiological substrate that enables people to remember their individual past. Two features of episodic memory--autonoetic consciousness, the self-aware ability to "travel through time", and one-trial learning, the acquisition of information in one occurrence of the event--raise important questions about the validity of animal models and the ability of unit recording studies to capture essential aspects of memory for episodes. We argue that autonoetic experience is a feature of human consciousness rather than an obligatory aspect of memory for episodes, and that episodic memory is reconstructive and thus its key features can be modeled in animal behavioral tasks that do not involve either autonoetic consciousness or one-trial learning. We propose that the most powerful strategy for investigating neurophysiological mechanisms of episodic memory entails recording unit activity in brain areas homologous to those required for episodic memory in humans (e.g., hippocampus and prefrontal cortex) as animals perform tasks with explicitly defined episodic-like aspects. Within this framework, empirical data suggest that the basic structure of episodic memory is a temporally extended representation that distinguishes the beginning from the end of an event. Future research is needed to fully understand how neural encodings of context, sequences of items/events, and goals are integrated within mnemonic representations of autobiographical events.

Action Potentials↗

PubMed2003

Prospective and retrospective memory coding in the hippocampus.

The effect of memory on hippocampal neuronal activity was assessed as rats performed a spatial task that was impaired by fornix lesions. The influences of current location, recently entered places, and places about to be entered were compared. Three new findings emerged. (1) Current, retrospective, and prospective coding were common and recorded simultaneously in neural ensembles. (2) The origin of journeys influenced firing even when rats made detours, showing that recent memory could modulate neuronal activity more than spatial trajectory. (3) Diminished retrospective coding and, more markedly, reduced prospective coding in error trials suggested that the neuronal signal was important for task performance. The population of hippocampal neurons thus encoded information about the recent past, the present, and the imminent future, consistent with a neuronal mechanism for episodic memory.

Animals↗

PubMed2003

Both dorsal and ventral hippocampus contribute to spatial learning in Long-Evans rats.

The hippocampus (HPC) may be functionally heterogeneous in supporting spatial learning in rats. Thus, dorsal but not ventral HPC lesions have been reported to impair acquisition in the Morris water task which consists of finding a submerged platform in a pool filled with opaque water. To further investigate the functional differences between dorsal and ventral HPC regions, we used a one-trial matching to position water task in which the submerged platform occupied a different position during each session. This task is very sensitive to HPC damage. The results show that either dorsal or ventral HPC NMDA lesions disrupt the rapid acquisition of new place information. The acquisition deficit diminishes with training in both lesion groups. The data thus suggest that the entire HPC axis is involved in acquisition of spatial information.

Animals↗