INTEGRATIVE CORTICAL–SUBCORTICAL CONNECTIVITY UNDERLYING COGNITIVE AND EMOTIONAL PROCESSING: EVIDENCE FROM EXPERIMENTAL TRACING AND HUMAN DIFFUSION IMAGING

Cognitive and emotional functions arise from distributed interactions among cortical, thalamic, limbic, and brainstem networks rather than from isolated modality-specific regions. Although individual connectivity pathways have been described, an integrative anatomical framework linking sensory, associative, motor, and arousal-related regions across species remains incomplete. In this study, we aim to synthesize experimental and human neuroimaging evidence to identify shared organizational principles of cortical–subcortical connectivity supporting cognitive and emotional processing. We used retrograde and anterograde tract-tracing techniques (Fluoro-Gold and biotinylated dextran amine) in rodents to map connections of the auditory cortex, insular cortex, supplementary motor area, and pedunculopontine nucleus. We compared experimental findings with high-resolution 3-tesla diffusion MRI tractography derived from healthy human datasets. Across regions, modality-related cortices exhibited extensive connectivity with higher-order thalamic nuclei, limbic structures, and brainstem arousal systems. The auditory cortex showed prominent connections with the amygdala, hippocampus, cingulate, and orbitofrontal cortices, supporting emotional modulation, learning, and decision-making. The insular cortex was strongly linked to intralaminar, midline, and ventral thalamic nuclei associated with salience detection, interoception, and affective processing. The supplementary motor area and pedunculopontine nucleus demonstrated connections with brainstem nuclei involved in arousal, motivation, and cognitive–motor integration. Human diffusion tractography largely corresponded with experimental findings, indicating cross-species conservation of these networks. These observations support a distributed connectivity model in which sensory and motor regions are embedded within broader cognitive–emotional and arousal networks. Our results highlight that integrating experimental tracing with human neuroimaging provides a robust framework for understanding network-level dysfunction in neuropsychiatric and neurodegenerative disorders.