Goal-oriented searching mediated by ventral hippocampus early in trial-and-error learning

Area of Science:

• Neuroscience
• Behavioral Biology
• Systems Neuroscience

Background:

• Behavioral learning, often trial-and-error, is fundamental but its neural underpinnings are unclear.
• The hippocampus is crucial for learning and memory, but functional specialization across its subdivisions is not fully understood.

Purpose of the Study:

• To investigate the specific and sequential roles of hippocampal subdivisions in trial-and-error maze navigation.
• To understand how neural changes, specifically feedforward inhibitory connectivity (FFI), relate to learning phase transitions.

Main Methods:

• Utilized lesion studies targeting ventral, intermediate, and dorsal hippocampus in mice during maze navigation tasks.
• Monitored behavioral learning phases and correlated them with changes in feedforward inhibitory connectivity (FFI) within hippocampal subdivisions.

Main Results:

• Ventral hippocampus (vH) mediates early goal-oriented searching, with FFI growth in vH preceding behavioral learning.
• Learning progresses through discrete phases characterized by specific search habits, with transitions linked to sequential FFI growth from ventral to dorsal hippocampus.
• Lesions in specific hippocampal subdivisions impaired corresponding learning stages (vH: early learning; intermediate: intermediate place learning; dorsal: late spatial learning).

Conclusions:

• Navigational trial-and-error learning involves a stereotyped sequence of subtasks mediated by distinct hippocampal subdivisions.
• Ventral hippocampus (vH), due to its connectivity, may link specific goals to internal states, impacting learning in both healthy and pathological conditions.