Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears.--Hippocrates (5th Century, B.C.; quoted in Kandel et al. 1991:iv)
Neuro term. 1. Those circuits, centers, and modules of the central nervous system which are involved in sending, receiving, and processing speechless signs. 2. In right-handed individuals, modules of the right brain cerebral hemisphere, considered to be more nonverbal, holistic, visuospatial, and intuitive than the verbal, analytic, sequential, and rational left brain hemisphere (see HUMAN BRAIN, Right brain, left brain). 3. Those ancient centers (e.g., nuclei) and paleocircuits of the nervous system which evolved in vertebrates--from the jawless fishes to human ancestors (e.g., Homo habilis)--for communication before the advent of speech.
Usage: Just as the brain's newer speech centers (e.g., Broca's area) control language communication, earlier areas of the nonverbal brain control communication apart from words. Knowing its parts and wiring helps us decode nonverbal messages.
Media. "A skillful outline can be more appealing than a photographic image. The simple line appeals to the brain which has limited attention and limited abilities to process information rapidly." (San Diego Union-Tribune interview with UC-San Diego neuroscientist, Vilayanur Ramachandran [May 7, 1999, A1, A-19])
Literature. The first recorded verbal reference to the human brain is Egyptian (the word 'ys), written on papyrus in the 17th Century, B.C. (Kandel et al. 1991).
Evolution. Our nonverbal brain consists of six interrelated divisions, outlined below, which merged in an evolutionary process from ca. 500-to-two m.y.a.:
(1) AQUATIC BRAIN & SPINAL CORD: The oldest neural division, present in the jawless fishes, includes the spinal cord's interneuron pools and motor neuron pathways a. for tactile withdrawal, and b. for the rhythmic, oscillatory movements of swimming (and much later, for walking).
(2) AMPHIBIAN BRAIN: With amphibians, 1. the pontine reticular excitatory system becomes more elaborate. The pontine tegmentum's link to the spinal cord's anterior horn motor neurons and muscle spindles raised the body by exciting antigravity extensor muscles (see ANTIGRAVITY SIGN). 2. The vestibulospinal pathway elaborated--from receptors in the inner ear via the vestibular nerve (cranial VIII), and via cerebellar fibers to the vestibular nucleus in the upper medulla--running the length of the spinal cord for body posture (i.e., basic stance) in relation to gravity. 3. The tectospinal tract evolved, consisting of the superior (and inferior) colliculus and its links, via the brain stem, running a. to cervical cord interneurons, then b. to anterior horn motor neurons, then c. to spinal nerves, and finally reaching d. muscle spindles for postural reflexes to sights and sounds. 4. And the rubrospinal tract further evolved: paleocircuits from the red nucleus of the midbrain running a. to thoracic cord interneurons, then b. to anterior horn motor neurons, and finally c. to muscles and muscle spindles for postural tone of the limbs' flexor muscles.
(3) REPTILIAN BRAIN: With reptiles, 1. the vestibuloreticulospinal system evolvedto control axial and girdle muscles for posture relative to positions of the head. 2. The basal ganglia-ansa lenticularis pathway reverberated links between the amygdala and basal ganglia via the ansa lenticularis and lenticulate fasciculus to the midbrain tegmentum, red nucleus, and reticular system to spinal cord interneurons required for the high-stand display.
(4) MAMMALIAN BRAIN: With mammals, 1. the amygdalo-hypothalamic tract became more elaborate: the central amygdala's link to the hypothalamus, via the stria terminalis, provided wiring for defensive postures (see, e.g., BROADSIDE DISPLAY). 2. Hypothalamus-spinal cord pathways adapted as well: the hypothalamus's dorsomedial and ventromedial nuclei fed a. indirectly via the brain stem's reticular system, and b. directly through fiberlinks to lower brain-stem and spinal-cord circuits to cord motor neurons for emotion cues (see, e.g., ANGER). 3. The septo-hypothalamo-midbrain continuum evolved: the medial forebrain bundle (from the olfactory forebrain and limbic system's septal nuclei) via the hypothalamus's lateral nuclei to midbrain-tegmentum brain-stem motor centers, mediated emotions (see, e.g., FEAR). 4. The cingulate gyrus facial circuit evolved: links run from the anterior cingulate cortex a. to the hippocampus, b. to the amygdala, c. to the hypothalamus, and d. through the brain stem, finally e. to the vagus (cranial X) and facial (cranial VII) nerves which, respectively, control the larynx and facial muscles required for vocalizing and moving the lips.
(5) PRIMATE BRAIN: With primates, 1. the neocortex's corticospinal tract further evolved: the posterior parietal cortex linked to supplementary motor, premotor, and primary motor cortices (with basal-ganglia feedback loops) via the corticospinal tract, to cervical and thoracic anterior-horn spinal interneurons, and to motor neurons in control of arm, hand, and finger muscles for skilled movements of the precision grip. 2. Modules of the inferior temporal neocortex evolved to provide visual input a. to the occipital neocortex's parvocellular interblob system (V1 to V2 and V4), permitting recognition of complex shapes, and b. to the inferior temporal cortex permitting heightened responses to hands and the ability to recognize faces.
(6) HUMAN BRAIN: With hominids, 1. the corticobulbar tract further evolved: corticobulbar pathways to the facial nerve (cranial VII) permitted intentional facial expressions (see, e.g., SMILE). 2. Broca's cranial pathways evolved: Broca's-area neocircuits via corticobulbar pathways to multiple cranial nerves permitted speech. 3. And Broca's spinal pathways evolved: Broca's-area neocircuits via corticospinal pathways to cervical and thoracic spinal nerves permitted manual sign language and linguistic-like mime cues.