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Cerebrospinal fluid is the fluid occupying the brain ventricles and surrounding subarachnoid spaces. Production, movement and removal connect its composition and pressure to the function of several interfaces. It is not interchangeable with either blood or fluid inside neurons.

Coauthor of experiments expressing rat-brain messenger RNA in frog oocytes. Responses to neurotensin and acetylcholine connected experimentally supplied genetic information with measurable cellular signaling.^[ref]

A choroid plexus is a vascular and epithelial structure projecting into a brain ventricle and contributing to cerebrospinal fluid production. Its epithelial barrier separates blood-associated and ventricular compartments. Secretion is a regulated transport process rather than simple unfiltered leakage from vessels.

The cisterna magna is an enlarged subarachnoid space near the inferior cerebellum and dorsal medulla. It contains cerebrospinal fluid and connects with surrounding subarachnoid pathways. Its location distinguishes it from the ventricular cavities inside the brain.

Resources or strategies allowing performance to remain effective despite brain changes. A later clinical symptom onset can be compatible with reserve without implying a lower disease incidence or less underlying pathology.

Concern for another's suffering with an orientation toward helping. Compassion should not be inferred merely from unpleasant arousal or from regional brain activation.

A cranial nerve is one of the traditionally numbered neural pathways associated with the brain and head. The group contains sensory, motor and mixed pathways. Their developmental and central connections are not identical merely because they share the cranial-nerve designation.

A critical period in neural development is a bounded interval in which particular experiences have a strong role in establishing a specified function or circuit organization. Its timing must be stated for a species and a measured outcome. A sensitive period emphasizes heightened susceptibility without necessarily asserting that every later change is impossible.

A classic example comes from monocular deprivation in cats. P. B. Dews and colleagues closed one eye at different ages and for different durations, then compared vision through the two eyes when the animals were at least a year old. Starting deprivation at one month offered little protection against lasting impairment; starting at two months reduced the impairment, and starting at four months or later produced no lasting deficit detectable in their behavioural tests. The age comparison revealed a developmental window rather than merely a short-lived effect of having an eye closed.^[ref]

The design separates age at disruption, duration of disruption, and the function tested. A change in visual acuity and a change in the responses of visual cortex neurons need not have identical recovery profiles. The existence of a critical period for one visual measure does not establish a single deadline for the entire brain, or the absence of adult neuroplasticity.^[ref]

Coauthor of research on brain responses to skin warming and cooling. The study connected controlled thermal stimulation with regional signals measured by positron emission tomography in awake humans.^[ref]

The diencephalon is a division of the forebrain surrounding the third ventricle, deep beneath the cerebral hemispheres. It includes the thalamus, hypothalamus and epithalamus. The anatomical name groups several interacting regions: circuits of the thalamus connect with the cerebral cortex, while the hypothalamus coordinates aspects of homeostasis and regulates signals to the pituitary gland.^[ref]

The relation to the third ventricle gives a useful way to read a section of the brain. The paired thalami lie beside the narrow midline fluid space; the surrounding neural tissue belongs to the diencephalic region, while cerebrospinal fluid occupies the cavity. Distinguishing the cavity from its walls connects the ventricular system to the organization of the surrounding brain.^[ref]

Designer receptors used to alter cell signalling in response to an administered ligand. The name does not establish that the ligand is inert elsewhere or that its administered form is the chemical species acting in the brain.

The dura mater is the tough outermost meningeal covering of the brain and spinal cord. Its supporting and enclosing role differs from the delicate membranes bounding the cerebrospinal-fluid spaces. Cranial folds and venous channels add further structural organization to the covering.

The eastern phoebe, Sayornis phoebe, is a North American flycatcher belonging to Tyranni, the suboscine branch of Passeriformes. It often watches for flying insects from a low perch, then makes a short flight to capture prey. Sheltered ledges, including those on bridges and buildings, provide nesting sites. Feeding behavior and nest placement help identify the living species alongside its appearance and voice.^[ref]

Its vocal development provides a controlled test of learning. In a 1991 study, four nestlings collected at 10–12 days were hand-reared and deafened at about 35 days, before they began singing. Their later songs were judged normal in comparison with wild males and intact laboratory birds. The tested birds could therefore develop the species-typical song without auditory feedback from their own voices.^[ref]

The result is narrower than saying that the brain or experience has no role in singing. It tests whether intact hearing during this developmental interval is necessary for the measured song pattern. Comparing it with a songbird experiment in which removing auditory experience disrupts song makes the experimental question clear: similar adult behavior can arise through different developmental requirements.

Inflammation of brain tissue. Infection and immune-mediated processes are different causes, so the anatomical term does not establish one organism or mechanism.

Historical soft, brain-like malignant growth. The gross appearance does not specify one modern diagnosis in histology.

Destructive softening of brain tissue, often following cerebral infarction. Gross consistency does not establish its cause.

An ependymal cell is a cell of the ependyma, the lining of the brain ventricular system and central canal of the spinal cord. Many ventricular ependymal cells carry multiple motile cilia facing the cerebrospinal fluid. Their coordinated beating can move nearby fluid; the cells are distinct from the neurons whose signaling circuits surround the cavity.^[ref]

In a 2016 study, organized cilia modules in the mouse third ventricle generated structured fluid-flow networks and a periodically switching flow pattern.^[ref] The result illustrates how an epithelial lining can actively organize its fluid environment rather than simply delimit it. A cilium on one cell acts locally; tissue-level organization determines the collective transport pattern.

Tanycytes are specialized ependymal-related cells with long processes. Their geometry and functions should not be assigned indiscriminately to every ependymal cell.

Epilepsy is a brain disorder involving an enduring predisposition to epileptic seizures. The condition includes different seizure types and causes; a single seizure provoked by a temporary disturbance does not automatically establish it.

The distinction between an individual event and a continuing predisposition is important in both diagnosis and research. Counting events, classifying their mechanism and investigating the underlying cause answer different questions.^[ref]

An epileptic seizure is a transient event caused by abnormal excessive or synchronized activity in brain networks. Its manifestations depend on the recruited circuits and can include motor changes, altered sensation or impaired awareness.

The mechanism distinguishes it from a superficially similar event with another cause. Electroencephalography can supply physiological evidence, but the observed behavior and the clinical time course remain important to interpretation.

The forebrain, also called the prosencephalon in embryological terminology, is the anterior major division of the developing vertebrate brain. It subdivides into the telencephalon and diencephalon. The name describes a developmental and anatomical grouping, rather than one nucleus with a single task.^[ref]

The telencephalon includes the cerebral-hemisphere system, while the diencephalon includes regions such as the thalamus, hypothalamus and epithalamus. Thus the visible cerebral cortex is part of the forebrain but does not exhaust it. Deep nuclei and connecting pathways also belong to the region.^[ref]

The ventricular spaces provide an illuminating map. The lateral ventricles lie within the cerebral hemispheres, while the third ventricle is associated with the diencephalic region. A fluid-filled cavity and its surrounding neural tissue are different structures: locating the cavity helps orient the tissue, but does not make the cavity itself a neuron-processing center.^[ref]

This developmental grouping is useful when comparing brains whose proportions differ greatly. Expansion of one forebrain component does not erase the distinction among its components. Likewise, observing a response in the lateral habenula identifies activity in one forebrain circuit, not a computation performed uniformly by the entire forebrain.