Resolving a paradox about how vision is transformed into familiarity

Area of Science:

• Neuroscience
• Cognitive Science
• Psychology

Background:

• Humans and primates exhibit systematic differences in image memorability.
• Image memorability is linked to the neural signal of repetition suppression in the inferotemporal cortex (ITC).
• A conflict exists: reduced neural firing is linked to familiarity, yet more memorable images elicit greater firing in ITC.

Purpose of the Study:

• To resolve the paradox between repetition suppression and image memorability in neural signals.
• To investigate the roles of the inferotemporal cortex (ITC) and hippocampus (HC) in image familiarity and memory.
• To understand how the brain transforms visual perception into a sense of familiarity.

Main Methods:

• Compared neural activity in the ITC and HC of rhesus monkeys during a single-exposure image familiarity task.
• Analyzed neural responses to images with varying memorability.
• Utilized linear decoding to assess information present in ITC neural activity.

Main Results:

• The paradox was resolved in the hippocampus (HC), where neural representations showed a stronger memory signal for more memorable images.
• Hippocampal (HC) responses were otherwise unaffected by memorability, suggesting an isolated memory signal.
• Memorability could be decoded from inferotemporal cortex (ITC) activity using a decoder that accounted for memorability modulation.

Conclusions:

• The medial temporal lobe (MTL), particularly the hippocampus (HC), plays a crucial role in familiarity behavior.
• Inferotemporal cortex (ITC) signals related to familiarity are selectively extracted by medial temporal lobe (MTL) computations.
• These findings offer new insights into the neural mechanisms supporting familiarity and memory formation.