Where is the trace in trace conditioning?

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Cerebellar Function

Background:

• Cerebellar brain circuits for Pavlovian eyeblink conditioning were thought to be well-mapped by 2000.
• Recent findings necessitate further differentiation of cerebellar regions and mechanisms for delay and trace conditioning paradigms.
• Trace conditioning serves as a tractable model for studying declarative learning.

Purpose of the Study:

• To differentiate cerebellar regions and mechanisms involved in delay versus trace eyeblink conditioning.
• To investigate the role of forebrain regions and pontine-cerebellar nuclear connections in trace conditioning.
• To elucidate the cerebellar cortical mechanisms supporting delay conditioning.

Main Methods:

• Comparative analysis of cerebellar circuitry in delay and trace eyeblink conditioning.
• Examination of forebrain contributions via pontine-cerebellar nuclear pathways.
• Investigation of cerebellar cortical long-term depression-like processes.

Main Results:

• A temporal gap in trace conditioning engages forebrain dependencies and bypasses cerebellar cortex via pontine-cerebellar connections.
• Delay conditioning requires a cerebellar cortical long-term-depression-like process.
• Distinct cerebellar circuitry is differentially engaged during acquisition of delay and trace conditioned responses.

Conclusions:

• Cerebellar circuits for delay and trace conditioning are not uniform and require further detailed mapping.
• The temporal gap in trace conditioning highlights distinct neural substrates compared to delay conditioning.
• Understanding these differences provides insight into the brain mechanisms underlying different forms of learning.