This medical schematic diagram illustrates the functional neuroanatomy of the human basal ganglia circuitry, detailing the classic motor loops. The diagram displays key anatomical structures including the cerebral cortex, thalamus (violet), neostriatum (red/orange), globus pallidus externa (GPe, light blue), globus pallidus interna (GPi, bluish-gray), subthalamic nucleus (STN, dark blue), and substantia nigra pars compacta (SNc, dark gray). Three primary functional pathways are highlighted: the Direct Pathway (solid black lines from neostriatum to GPi), which facilitates movement via disinhibition of the thalamus; the Indirect Pathway (dashed black lines connecting neostriatum to GPe, then STN, and finally GPi), which serves to inhibit motor activity; and the Hyperdirect Pathway (solid blue line from cortex directly to STN), which provides rapid inhibition of motor output by bypassing the striatum. Arrows indicate the direction of signal flow between these nuclei and the thalamocortical circuit, providing a visual model for understanding movement disorders like Parkinson's and Huntington's disease where these pathways are imbalanced.

A pathophysiology diagram providing a schematic overview of the human basal ganglia motor circuits, specifically illustrating the indirect (left) and direct (right) pathways. The main illustration uses a coronal brain section to map anatomical structures: the cortex, striatum (caudate nucleus and putamen), thalamus, globus pallidus external (GPe) and internal (GPi) segments, subthalamic nucleus (STN), and substantia nigra (pars compacta, SNpc; pars reticulata, SNpr). Neurotransmission is color-coded: green arrows denote excitatory glutamatergic (GLU) or dopaminergic (DA) signals, while red T-bars signify inhibitory GABAergic (GABA/SP, GABA/ENK) signals. The direct pathway is labeled 'Motor Facilitation' and shows inhibitory projections from D1-receptor striatal neurons directly to the GPi/SNpr. The indirect pathway is labeled 'Motor Cessation' and highlights connections from D2-receptor striatal neurons to the GPe, subsequently influencing the STN and GPi/SNpr. An inset details projections to the SNpc, including inputs from the cortex, STN, and pedunculopontine nucleus (PPN). This educational material demonstrates the neuroanatomical basis for motor control and the circuit dysfunction relevant to Parkinson's disease (PD).

Educational medical diagram illustrating the pathophysiology of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) within the basal ganglia. The image is divided into three sections. On the left, a sagittal view of the human brain maps the four major dopaminergic pathways: nigrostriatal (blue), mesolimbic (red), tuberoinfundibular (green), and mesocortical (purple). The center and right panels provide a comparative schematic of basal ganglia circuitry. The 'Normal' circuit shows the functional balance between the direct and indirect pathways, highlighting the roles of the striatum (caudate and putamen), medium spiny neurons (MSNs), acetylcholine (Ach) interneurons, and the globus pallidus (externus and internus). In contrast, the 'PANDAS' circuit depicts neuroinflammation and cholinergic disruption in the dorsal striatum. This pathological state results in decreased Ach modulation and fewer distinct MSNs, leading to hyperactivity of the direct pathway. The diagram concludes by linking this physiological imbalance to clinical manifestations, including tics, obsessions, and compulsions typical of PANDAS syndrome.

This composite educational graphic details the neuroanatomy and connectivity of the basal ganglia network, specifically focusing on the fronto-striatal circuit. It consists of a functional schematic diagram paired with MRI diffusion tractography images. The schematic illustrates key nodes including the Striatum (containing D1 and D2 pathways), Substantia Nigra, Thalamus (VL/VA/MD nuclei), Globus Pallidus (EP/IP), and the Subthalamic Nucleus (STN). Arrows indicate excitatory and inhibitory pathways, highlighting the indirect and direct pathways of motor control relevant to Parkinson's disease. The accompanying MRI panels (coronal, sagittal, and axial views) show white matter fiber reconstruction using tractography. These panels visualize axonal connections between the striatum and thalamic nuclei, color-coded in blue and yellow to represent distinct fiber bundles. The resource is designed to teach the neurobiological basis of extrapyramidal signs and the localization of basal ganglia dysfunction in clinical neurology.

An anatomical diagram illustrating the cytoarchitecture of the human cerebellum at both macroscopic and cellular scales. The left panel shows a cross-section of the cerebellar cortex with its characteristic folia. It identifies three primary layers: the central white matter (WM) core, the intermediate granular layer (GL), and the superficial molecular layer (ML). A black inset box indicates the transition to the high-magnification view on the right. The magnified cellular schematic depicts the organized histological layers: the deep fiber tracts (FT); the dense granular layer containing numerous small granular cells (GC) and larger Golgi cells (GgC); a distinct boundary composed of a single row of large, flask-shaped Purkinje cell (PC) bodies; and the outermost molecular layer featuring basket cells (BC) and molecular cells (MC). The diagram highlights the spatial relationship between these neurons, specifically the Purkinje cell dendrites extending into the molecular layer. This illustration is intended for educational purposes in neuroanatomy and virtual histology.

This composite image provides a comparative anatomical and pathological view of the human cerebellum across three modalities. Panel A presents a high-resolution 7-Tesla MRI scan, highlighting the distinct three-layered architecture of the cerebellar cortex and the characteristic serrated, or 'zick-zack', morphology of the dentate nucleus with high contrast. Panel B shows a corresponding gross anatomical specimen of the same cerebellum, formalin-fixed, displaying the physical arrangement of the folia and the internal white matter (arbor vitae) in a natural state. Panel C is a histological section stained with Hematoxylin and Eosin (H&E), providing a microscopic correlation of the dentate nucleus and adjacent cerebellar cortex. This stained section differentiates cellular layers by purple and pink hues, illustrating the microscopic folding and cellular density of the deep cerebellar nuclei. This comparison is clinically relevant for neuroradiology and neuropathology, demonstrating how advanced imaging correlates with gross anatomy and histopathology to identify structural integrity or neurodegenerative changes in the posterior fossa.

Educational neuroanatomical diagram comparing the macroarchitecture of rodent and primate cerebella. Panel A (top) illustrates the rodent cerebellum in dorsal and parasagittal views, highlighting the deep cerebellar nuclei (CN): the medial (fastigial), intermediate (interposed/globose and emboliform), and lateral (dentate) nuclei. The inset contrasts the smooth rodent lateral nucleus with the highly convoluted primate dentate nucleus. Anatomical regions including the vermis, hemispheres, and lobules (I-X) are labeled. Arrows indicate Purkinje cell outputs to the CN and efferent projections to the brainstem and cortex. Panel B (bottom) displays the mouse cerebellum highlighting molecular topography through Zebrin II banding. The left side shows alternating Zebrin-positive and negative parasagittal stripes. The right side illustrates a midline parasagittal section divided into functional transverse zones: anterior, central, posterior, and nodular. This visual resource aids in understanding evolutionary neuroanatomy, cerebellar circuitry, and zonal molecular patterning.

This medical diagram provides a schematic representation of the cerebello-thalamo-cerebro-cortical circuits (CTCCs) within a sagittal view of the human brain. The illustration highlights the bidirectional connectivity between the cerebellum and several telencephalic regions. Key nodes include the deep cerebellar nuclei (DCN), which project via the red nucleus (RN) and anterior thalamic nucleus (ATN) to the motor cortex (MC), prefrontal cortex (PFC), parietal cortex (PC), and temporal cortex (TC). Afferent pathways demonstrate that cortical regions and the basal ganglia—specifically involving the subthalamic nucleus (STN)—relay information back to the cerebellum through the anterior pontine nuclei (APN). The use of color-coded arrows illustrates the complex feedback loops: green arrows represent cerebellar outputs and intrinsic connections, while red and brown arrows depict descending cortical and basal ganglia inputs. This circuit demonstrates the anatomical basis for the cerebellum’s role in coordinating both motor planning and higher-order cognitive functions across different functional domains.