Mega-scale movie-fields in the mouse visuo-hippocampal network

Area of Science:

• Neuroscience
• Cognitive Science
• Computational Neuroscience

Background:

• Natural visual experience comprises continuous, related images during immobility.
• The hippocampus is vital for episodic memory, but studies often require active exploration.
• Understanding cortico-hippocampal circuit processing of visual episodes is crucial.

Purpose of the Study:

• To investigate neural responses to visual stimuli in head-fixed mice without task demands.
• To explore how the cortico-hippocampal circuit processes visual episodes.
• To compare hippocampal and visual cortical neuronal activity during movie viewing.

Main Methods:

• Recorded neural activity in head-fixed mice viewing a silent movie (Allen Brain Observatory).
• Analyzed neuronal selectivity and firing patterns in hippocampal and visual cortical regions.
• Compared responses to continuous versus scrambled movie sequences.

Main Results:

• A significant portion of hippocampal neurons (33%) and nearly all visual neurons (97%) exhibited movie-selectivity, forming 'movie-fields'.
• Movie-tuning persisted regardless of mouse immobility or locomotion.
• Hippocampal neurons encoded continuous sequences more strongly than visual cortical neurons, as evidenced by fewer, broader movie-fields and abolished selectivity to scrambled sequences.

Conclusions:

• The hippocampus demonstrates a greater capacity for continuous visual sequence encoding compared to visual areas.
• Movie viewing provides a viable method to study episodic information processing and memory mechanisms across brain regions, even in immobile subjects.
• Findings support the role of the hippocampus in episodic sequence encoding.