Perceptual learning, awareness, and the hippocampus.

Area of Science:

• Neuroscience
• Cognitive Psychology

Background:

• Declarative memory relies on the hippocampus and medial temporal lobe.
• Declarative memory is typically accessible to conscious recall.
• Previous research suggested medial temporal lobe damage impairs perceptual learning without conscious awareness.

Purpose of the Study:

• To investigate the role of the hippocampal formation in nonconscious perceptual learning.
• To determine if hippocampus-dependent memory is accessible to conscious recollection.
• To clarify the effects of medial temporal lobe damage on perceptual learning.

Main Methods:

• Utilized a perceptual learning task previously employed in similar studies.
• Examined patients with focal hippocampal formation damage.
• Assessed patients with more extensive medial temporal lobe and lateral temporal cortex damage.

Main Results:

• Perceptual learning remained intact in individuals with damage confined to the hippocampal formation.
• These findings suggest that damage limited to the hippocampal formation does not impair nondeclarative (nonconscious) memory.
• Perceptual learning was impaired in patients with extensive medial temporal lobe damage.

Conclusions:

• Damage restricted to the hippocampal formation does not impede nonconscious memory processes.
• The data support the notion that hippocampus-dependent memory is consciously accessible.
• Extensive medial temporal lobe damage, including lateral temporal cortex, negatively impacts perceptual learning.