Altered visual processing in a rodent model of Attention-Deficit Hyperactivity Disorder

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Animal Models of Disease

Background:

• Attention-Deficit Hyperactivity Disorder (ADHD) is characterized by distractibility, potentially linked to the superior colliculus (SC).
• Evidence suggests altered SC functioning in ADHD, with a hyper-responsive SC proposed to mediate core symptoms.

Purpose of the Study:

• To systematically characterize the superior colliculus (SC) in spontaneously hypertensive rats (SHR), a validated animal model for ADHD.
• To investigate collicular-dependent behavior, neural activity, and morphology in SHRs compared to control strains.

Main Methods:

• Assessed collicular-dependent orienting behavior in SHRs and control strains (Wistar Kyoto and Wistar).
• Recorded local field potential (LFP) and multiunit activity in response to visual stimuli in anesthetized rats.
• Examined morphological measures including SC volume, neuron and glia densities, and glia:neuron ratio.

Main Results:

• SHRs exhibited prolonged responsiveness and longer response duration to repeated visual stimuli compared to controls.
• SHRs displayed hyper-responsive LFP and multiunit activity in the superficial SC layers, not attributable to retinocollicular pathway changes.
• SHRs showed a reduced glia:neuron ratio in the SC compared to WKY rats, potentially explaining heightened responsiveness.

Conclusions:

• This study reveals strain-specific alterations in SC function and structure in SHRs.
• Findings provide convergent evidence supporting a role for SC dysfunction in ADHD pathophysiology.