"Brain" - what is it, definition of the term
The term «brain» designates the soft, highly vascularized tissue enclosed by the skull that processes sensory information, generates motor commands, and controls autonomic functions; in rodents such as rats and mice it comprises cerebral hemispheres, cerebellum, brainstem, and associated nuclei, organized into neuronal and glial networks that underlie behavior and physiological regulation.
Detailed information
The cerebral organ of rodents, specifically the laboratory species commonly referred to as rats and mice, exhibits a compact yet highly organized structure that supports a range of sensory, motor, and cognitive processes. The dorsal region comprises the neocortex, arranged in six distinct layers, each characterized by unique neuronal populations and connectivity patterns. The ventral portion includes the hippocampus, amygdala, and basal ganglia, which together regulate memory formation, emotional responses, and motor planning. Subcortical structures such as the thalamus and hypothalamus integrate autonomic functions and endocrine regulation.
Developmental progression follows a well‑defined timeline. Early embryonic stages involve neurogenesis within the ventricular zone, producing progenitor cells that migrate radially to form cortical layers. Postnatal maturation includes synaptic pruning, myelination, and the refinement of excitatory and inhibitory circuits. By adulthood, the organ reaches a stable configuration that enables complex behaviors observed in experimental paradigms.
Key physiological attributes include:
- High neuronal density: approximately 10⁸ neurons in the mouse and 2 × 10⁸ in the rat, surpassing many larger mammals on a per‑gram basis.
- Distinct neurotransmitter systems: dopamine, glutamate, GABA, and acetylcholine pathways are conserved, allowing translational studies of pharmacological agents.
- Robust plasticity: long‑term potentiation and depression are readily induced in hippocampal slices, providing a reliable model for learning‑related mechanisms.
Research applications capitalize on the organ’s accessibility and genetic tractability. Transgenic lines enable cell‑type‑specific labeling, optogenetic manipulation, and real‑time calcium imaging. Behavioral assays—such as maze navigation, fear conditioning, and social interaction—correlate neural activity patterns with functional outcomes. Moreover, disease models (e.g., Alzheimer‑type pathology, Parkinsonian degeneration) exploit the organ’s susceptibility to protein aggregation and neuroinflammation, offering insight into therapeutic interventions.
Methodological considerations emphasize precise stereotaxic targeting, adequate anesthesia protocols, and post‑mortem tissue preservation. Histological techniques, including Nissl staining and immunohistochemistry, reveal cytoarchitectural boundaries, while electrophysiological recordings capture real‑time firing dynamics. Advanced imaging modalities, such as two‑photon microscopy and magnetic resonance spectroscopy, provide non‑invasive assessment of metabolic and structural changes.
In comparative context, the rodent organ shares fundamental organizational principles with that of larger mammals, yet exhibits species‑specific differences in cortical folding, neuronal subpopulation ratios, and synaptic density. These variations inform the selection of appropriate models for particular neurological questions, ensuring that experimental findings translate effectively across taxa.