Vocabulary

Abducens nucleus: A group of excitatory motor neurons in the medial brainstem that send projections through the VIth cranial nerve to control the ipsilateral lateral rectus muscle. In addition, abducens interneurons send an excitatory projection across the midline to a subdivision of cells in the ipsilateral oculomotor nucleus, which project through the IIIrd cranial nerve to innervate the ipsilateral medial rectus muscle.
Absolute threshold: The smallest amount of stimulation needed for detection by a sense.
Acetylcholine: An organic compound neurotransmitter consisting of acetic acid and choline. Depending upon the receptor type, acetycholine can have excitatory, inhibitory, or modulatory effects.
Afferent nerve fibers: Single neurons that innervate the receptor hair cells and carry vestibular signals to the brain as part of the vestibulocochlear nerve (cranial nerve VIII).
A-fibers: Fast-conducting sensory nerves with myelinated axons. Larger diameter and thicker myelin sheaths increases conduction speed. Aβ-fibers conduct touch signals from low-threshold mechanoreceptors with a velocity of 80 m/s and a diameter of 10 μm; Aδ-fibers have a diameter of 2.5 μm and conduct cold, noxious, and thermal signals at 12 m/s. The third and fastest conducting A-fiber is the Aα, which conducts proprioceptive information with a velocity of 120 m/s and a diameter of 20 μm.
Agnosia: Loss of the ability to perceive stimuli.
Allodynia: Pain due to a stimulus that does not normally provoke pain, e.g., when a light, stroking touch feels painful.
Analgesia: Pain relief.
Anosmia: Loss of the ability to smell.
Aspartate: An excitatory amino acid neurotransmitter that is widely used by vestibular receptors, afferents, and many neurons in the brain.
Audition: Ability to process auditory stimuli. Also called hearing.
Auditory canal: Tube running from the outer ear to the middle ear.
Auditory hair cells: Receptors in the cochlea that transduce sound into electrical potentials.
Binocular advantage: Benefits from having two eyes as opposed to a single eye.
Binocular disparity: Difference is images processed by the left and right eyes.
Binocular vision: Our ability to perceive 3D and depth because of the difference between the images on each of our retinas.
Bottom-up processing: Building up to perceptual experience from individual pieces.
Bouncing balls illusion: The tendency to perceive two circles as bouncing off each other if the moment of their contact is accompanied by an auditory stimulus.
C-fibers: C-fibers: Slow-conducting unmyelinated thin sensory afferents with a diameter of 1 μm and a conduction velocity of approximately 1 m/s. C-pain fibers convey noxious, thermal, and heat signals; C-tactile fibers convey gentle touch, light stroking.
Chemical senses: Our ability to process the environmental stimuli of smell and taste.
Chronic pain: Persistent or recurrent pain, beyond usual course of acute illness or injury; sometimes present without observable tissue damage or clear cause.
Clock time: Scheduling activities according to the time on the clock.
Cochlea: Spiral bone structure in the inner ear containing auditory hair cells.
Cochlea: Snail-shell-shaped organ that transduces mechanical vibrations into neural signals.
Compensatory reflexes: A stabilizing motor reflex that occurs in response to a perceived movement, such as the vestibuloocular reflex, or the postural responses that occur during running or skiing.
Conditioned aversions and preferences: Likes and dislikes developed through associations with pleasurable or unpleasurable sensations.
Cones: Photoreceptors that operate in lighted environments and can encode fine visual details. There are three different kinds (S or blue, M or green and L or red) that are each sensitive to slightly different types of light. Combined, these three types of cones allow you to have color vision.
Cones: Photoreceptors of the retina sensitive to color. Located primarily in the fovea.
Contrast: Relative difference in the amount and type of light coming from two nearby locations.
Contrast gain: Process where the sensitivity of your visual system can be tuned to be most sensitive to the levels of contrast that are most prevalent in the environment.
C-pain or Aδ-fibers: C-pain fibers convey noxious, thermal, and heat signals
Crossmodal phenomena: Effects that concern the influence of the perception of one sensory modality on the perception of another.
Crossmodal receptive field: A receptive field that can be stimulated by a stimulus from more than one sensory modality.
Crossmodal stimulus: A stimulus with components in multiple sensory modalties that interact with each other.
C-tactile fibers: C-tactile fibers convey gentle touch, light stroking
Cutaneous senses: The senses of the skin: tactile, thermal, pruritic (itchy), painful, and pleasant.
Dark adaptation: Adjustment of eye to low levels of light.
Dark adaptation: Process that allows you to become sensitive to very small levels of light, so that you can actually see in the near-absence of light.
Depolarized: When receptor hair cells have mechanically gated channels open, the cell increases its membrane voltage, which produces a release of neurotransmitter to excite the innervating nerve fiber.
Descending pain modulatory system: A top-down pain-modulating system able to inhibit or facilitate pain. The pathway produces analgesia by the release of endogenous opioids. Several brain structures and nuclei are part of this circuit, such as the frontal lobe areas of the anterior cingulate cortex, orbitofrontal cortex, and insular cortex; and nuclei in the amygdala and the hypothalamus, which all project to a structure in the midbrain called the periaqueductal grey (PAG). The PAG then controls ascending pain transmission from the afferent pain system indirectly through the rostral ventromedial medulla (RVM) in the brainstem, which uses ON- and OFF-cells to inhibit or facilitate nociceptive signals at the spinal dorsal horn.
Detection thresholds: The smallest amount of head motion that can be reliably reported by an observer.
Dichotic listening: A task in which different audio streams are presented to each ear. Typically, people are asked to monitor one stream while ignoring the other.
Differential threshold (or difference threshold): The smallest difference needed in order to differentiate two stimuli. (See Just Noticeable Difference (JND))
Directional tuning: The preferred direction of motion that hair cells and afferents exhibit where a peak excitatory response occurs and the least preferred direction where no response occurs. Cells are said to be “tuned” for a best and worst direction of motion, with in-between motion directions eliciting a lesser but observable response.
Dorsal pathway: Pathway of visual processing. The “where” pathway.
Double flash illusion: The false perception of two visual flashes when a single flash is accompanied by two auditory beeps.
Endorphin: An endogenous morphine-like peptide that binds to the opioid receptors in the brain and body; synthesized in the body’s nervous system.
Exteroception: The sense of the external world, of all stimulation originating from outside our own bodies.
False memories: Memory for an event that never actually occurred, implanted by experimental manipulation or other means.
Flavor: The combination of smell and taste.
Foils: Any member of a lineup (whether live or photograph) other than the suspect.
Gamma-aminobutyric acid: A major inhibitory neurotransmitter in the vestibular commissural system.
Gaze stability: A combination of eye, neck, and head responses that are all coordinated to maintain visual fixation (fovea) upon a point of interest.
Glutamate: An excitatory amino acid neurotransmitter that is widely used by vestibular receptors, afferents, and many neurons in the brain.
Gustation: The action of tasting; the ability to taste.
Gustation: Ability to process gustatory stimuli. Also called taste.
Hair cells: The receptor cells of the vestibular system. They are termed hair cells due to the many hairlike cilia that extend from the apical surface of the cell into the gelatin membrane. Mechanical gated ion channels in the tips of the cilia open and close as the cilia bend to cause membrane voltage changes in the hair cell that are proportional to the intensity and direction of motion.
Hyperpolarizes: When receptor hair cells have mechanically gated channels close, the cell decreases its membrane voltage, which produces less release of neurotransmitters to inhibit the innervating nerve fiber.
Inattentional blindness: The failure to notice a fully visible, but unexpected, object or event when attention is devoted to something else.
Inattentional deafness: The auditory analog of inattentional blindness. People fail to notice an unexpected sound or voice when attention is devoted to other aspects of a scene.
Integrated: The process by which the perceptual system combines information arising from more than one modality.
Interaural differences: Differences (usually in time or intensity) between the two ears.
Interoception: The sense of the physiological state of the body. Hunger, thirst, temperature, pain, and other sensations relevant to homeostasis. Visceral input such as heart rate, blood pressure, and digestive activity give rise to an experience of the body’s internal states and physiological reactions to external stimulation. This experience has been described as a representation of “the material me,” and it is hypothesized to be the foundation of subjective feelings, emotion, and self-awareness.
Just noticeable difference (JND): The smallest difference needed in order to differentiate two stimuli. (see Differential Threshold)
Lateral inhibition: A signal produced by a neuron aimed at suppressing the response of nearby neurons.
Lateral rectus muscle: An eye muscle that turns outward in the horizontal plane.
Lateral vestibulo-spinal tract: Vestibular neurons that project to all levels of the spinal cord on the ipsilateral side to control posture and balance movements.
Light adaptation: Adjustment of eye to high levels of light.
Ma: Japanese way of thinking that emphasizes attention to the spaces between things rather than the things themselves.
McGurk effect: An effect in which conflicting visual and auditory components of a speech stimulus result in an illusory percept.
Mechanically gated ion channels: Ion channels located in the tips of the stereocilia on the receptor cells that open/close as the cilia bend toward the tallest/smallest cilia, respectively. These channels are permeable to potassium ions, which are abundant in the fluid bathing the top of the hair cells.
Mechanoreceptors: Mechanical sensory receptors in the skin that response to tactile stimulation.
Medial vestibulo-spinal tract: Vestibular nucleus neurons project bilaterally to cervical spinal motor neurons for head and neck movement control. The tract principally functions in gaze direction and stability during motion.
Misinformation effect: A memory error caused by exposure to incorrect information between the original event (e.g., a crime) and later memory test (e.g., an interview, lineup, or day in court).
Mock witnesses: A research subject who plays the part of a witness in a study.
Monochronic (M-time): Monochronic thinking focuses on doing one activity, from beginning to completion, at a time.
Multimodal: Of or pertaining to multiple sensory modalities.
Multimodal perception: The effects that concurrent stimulation in more than one sensory modality has on the perception of events and objects in the world.
Multimodal perception: The effects that concurrent stimulation in more than one sensory modality has on the perception of events and objects in the world.
Multimodal phenomena: Effects that concern the binding of inputs from multiple sensory modalities.
Multisensory convergence zones: Regions in the brain that receive input from multiple unimodal areas processing different sensory modalities.
Multisensory enhancement: See “superadditive effect of multisensory integration.”
Neurotransmitters: A chemical compound used to send signals from a receptor cell to a neuron, or from one neuron to another. Neurotransmitters can be excitatory, inhibitory, or modulatory and are packaged in small vesicles that are released from the end terminals of cells.
Nociception: Our ability to sense pain.
Nociception: The neural process of encoding noxious stimuli, the sensory input from nociceptors. Not necessarily painful, and crucially not necessary for the experience of pain.
Nociceptors: High-threshold sensory receptors of the peripheral somatosensory nervous system that are capable of transducing and encoding noxious stimuli. Nociceptors send information about actual or impending tissue damage to the brain. These signals can often lead to pain, but nociception and pain are not the same.
Noxious stimulus: A stimulus that is damaging or threatens damage to normal tissues.
Ocial touch hypothesis: Proposes that social touch is a distinct domain of touch. C-tactile afferents form a special pathway that distinguishes social touch from other types of touch by selectively firing in response to touch of social-affective relevance; thus sending affective information parallel to the discriminatory information from the Aβ-fibers. In this way, the socially relevant touch stands out from the rest as having special positive emotional value and is processed further in affect-related brain areas such as the insula.
Oculomotor nuclei: Includes three neuronal groups in the brainstem, the abducens nucleus, the oculomotor nucleus, and the trochlear nucleus, whose cells send motor commands to the six pairs of eye muscles.
Oculomotor nucleus: A group of cells in the middle brainstem that contain subgroups of neurons that project to the medial rectus, inferior oblique, inferior rectus, and superior rectus muscles of the eyes through the 3rd cranial nerve.
Odorants: Chemicals transduced by olfactory receptors.
Olfaction: Ability to process olfactory stimuli. Also called smell.
Olfaction: The sense of smell; the action of smelling; the ability to smell.
Olfactory epithelium: Organ containing olfactory receptors.
Omnivore: A person or animal that is able to survive by eating a wide range of foods from plant or animal origin.
Opponent Process Theory: Theory of color vision that assumes there are four different basic colors, organized into two pairs (red/green and blue/yellow) and proposes that colors in the world are encoded in terms of the opponency (or difference) between the colors in each pair. There is an additional black/white pair responsible for coding light contrast.
Opponent-process theory: Theory proposing color vision as influenced by cells responsive to pairs of colors.
Orthonasal olfaction: Perceiving scents/smells introduced via the nostrils.
Ossicles: A collection of three small bones in the middle ear that vibrate against the tympanic membrane.
Otoconia: Small calcium carbonate particles that are packed in a layer on top of the gelatin membrane that covers the otolith receptor hair cell stereocilia.
Otolith receptors: Two inner ear vestibular receptors (utricle and saccule) that transduce linear accelerations and head tilt relative to gravity into neural signals that are then transferred to the brain.
Pace of life: The frequency of events per unit of time; also referred to as speed or tempo.
Pain: Defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage,” according to the International Association for the Study of Pain.
Perception: The psychological process of interpreting sensory information.
Phantom limb: The perception that a missing limb still exists.
Phantom limb pain: Pain in a limb that no longer exists.
Phantom pain: Pain that appears to originate in an amputated limb.
Photo spreads: A selection of normally small photographs of faces given to a witness for the purpose of identifying a perpetrator.
Photoactivation: A photochemical reaction that occurs when light hits photoreceptors, producing a neural signal.
Pinna: Outermost portion of the ear.
Pinna: Visible part of the outer ear.
Placebo effect: Effects from a treatment that are not caused by the physical properties of a treatment but by the meaning ascribed to it. These effects reflect the brain’s own activation of modulatory systems, which is triggered by positive expectation or desire for a successful treatment. Placebo analgesia is the most well-studied placebo effect and has been shown to depend, to a large degree, on opioid mechanisms. Placebo analgesia can be reversed by the pharmacological blocking of  opioid receptors. The word “placebo” is probably derived from the Latin word “placebit” (“it will please”).
Polychronic (P-time): Polychronic thinking switches back and forth among multiple activities as the situation demands.
Primary auditory cortex: A region of the cortex devoted to the processing of simple auditory information.
Primary auditory cortex: Area of the cortex involved in processing auditory stimuli.
Primary somatosensory cortex: Area of the cortex involved in processing somatosensory stimuli.
Primary visual cortex: Area of the cortex involved in processing visual stimuli.
Primary visual cortex: A region of the cortex devoted to the processing of simple visual information.
Primary visual cortex (V1): Brain region located in the occipital cortex (toward the back of the head) responsible for processing basic visual information like the detection, thickness, and orientation of simple lines, color, and small-scale motion.
Principle of Inverse Effectiveness: The finding that, in general, for a multimodal stimulus, if the response to each unimodal component (on its own) is weak, then the opportunity for multisensory enhancement is very large. However, if one component—by itself—is sufficient to evoke a strong response, then the effect on the response gained by simultaneously processing the other components of the stimulus will be relatively small.
Principle of inverse effectiveness: The finding that, in general, for a multimodal stimulus, if the response to each unimodal component (on its own) is weak, then the opportunity for multisensory enhancement is very large. However, if one component—by itself—is sufficient to evoke a strong response, then the effect on the response gained by simultaneously processing the other components of the stimulus will be relatively small.
Proprioceptive: Sensory information regarding muscle position and movement arising from receptors in the muscles, tendons, and joints.
Receptive field: The portion of the world to which a neuron will respond if an appropriate stimulus is present there.
Retina: Cell layer in the back of the eye containing photoreceptors.
Retronasal olfaction: Perceiving scents/smells introduced via the mouth/palate.
Rods: Photoreceptors that are very sensitive to light and are mostly responsible for night vision.
Rods: Photoreceptors of the retina sensitive to low levels of light. Located around the fovea.
Rubber hand illusion: The false perception of a fake hand as belonging to a perceiver, due to multimodal sensory information.
Schema (plural: schemata): A memory template, created through repeated exposure to a particular class of objects or events.
Selective listening: A method for studying selective attention in which people focus attention on one auditory stream of information while deliberately ignoring other auditory information.
Semicircular canals: A set of three inner ear vestibular receptors (horizontal, anterior, posterior) that transduce head rotational accelerations into head rotational velocity signals that are then transferred to the brain. There are three semicircular canals in each ear, with the major planes of each canal being orthogonal to each other.
Sensation: The physical processing of environmental stimuli by the sense organs.
Sensitization: Increased responsiveness of nociceptive neurons to their normal input and/or recruitment of a response to normally subthreshold inputs. Clinically, sensitization may only be inferred indirectly from phenomena such as hyperalgesia or allodynia. Sensitization can occur in the central nervous system (central sensitization) or in the periphery (peripheral sensitization).
Sensory adaptation: Decrease in sensitivity of a receptor to a stimulus after constant stimulation.
Sensory modalities: A type of sense; for example, vision or audition.
Shape theory of olfaction: Theory proposing that odorants of different size and shape correspond to different smells.
Signal detection: Method for studying the ability to correctly identify sensory stimuli.
Silent language: Cultural norms of time and time use as they pertain to social communication and interaction.
Social time: Scheduling by the flow of the activity. Events begin and end when, by mutual consensus, participants “feel” the time is right.
Social touch hypothesis: Proposes that social touch is a distinct domain of touch. C-tactile afferents form a special pathway that distinguishes social touch from other types of touch by selectively firing in response to touch of social-affective relevance; thus sending affective information parallel to the discriminatory information from the Aβ-fibers. In this way, the socially relevant touch stands out from the rest as having special positive emotional value and is processed further in affect-related brain areas such as the insula.
Somatosensation: Ability to sense touch, pain and temperature.
Somatosensory cortex: Consists of primary sensory cortex (S1) in the postcentral gyrus in the parietal lobes and secondary somatosensory cortex (S2), which is defined functionally and found in the upper bank of the lateral sulcus, called the parietal operculum. Somatosensory cortex also includes parts of the insular cortex.
Somatotopic map: Organization of the primary somatosensory cortex maintaining a representation of the arrangement of the body.
Somatotopically organized: When the parts of the body that are represented in a particular brain region are organized topographically according to their physical location in the body (see Figure 2 illustration).
Sound waves: Changes in air pressure. The physical stimulus for audition.
Spatial principle of multisensory integration: The finding that the superadditive effects of multisensory integration are observed when the sources of stimulation are spatially related to one another.
Spinothalamic tract: Runs through the spinal cord’s lateral column up to the thalamus. C-fibers enter the dorsal horn of the spinal cord and form a synapse with a neuron that then crosses over to the lateral column and becomes part of the spinothalamic tract.
Stereocilia: Hairlike projections from the top of the receptor hair cells. The stereocilia are arranged in ascending height and when displaced toward the tallest cilia, the mechanical gated channels open and the cell is excited (depolarized). When the stereocilia are displaced toward the smallest cilia, the channels close and the cell is inhibited (hyperpolarized).
Superadditive effect of multisensory integration: The finding that responses to multimodal stimuli are typically greater than the sum of the independent responses to each unimodal component if it were presented on its own.
Superadditive effect of multisensory integration: The finding that responses to multimodal stimuli are typically greater than the sum of the independent responses to each unimodal component if it were presented on its own.
Synesthesia: The blending of two or more sensory experiences, or the automatic activation of a secondary (indirect) sensory experience due to certain aspects of the primary (direct) sensory stimulation.
Tastants: Chemicals transduced by taste receptor cells.
Taste receptor cells: Receptors that transduce gustatory information.
Temporal perspective: The extent to which we are oriented toward the past, present, and future.
Top-down processing: Experience influencing the perception of stimuli.
Torsion: A rotational eye movement around the line of sight that consists of a clockwise or counterclockwise direction.
Transduction: The conversion of one form of energy into another.
Transduction: The mechanisms that convert stimuli into electrical signals that can be transmitted and processed by the nervous system. Physical or chemical stimulation creates action potentials in a receptor cell in the peripheral nervous system, which is then conducted along the axon to the central nervous system.
Trichromacy theory: Theory that proposes that all of your color perception is fundamentally based on the combination of three (not two, not four) different color signals.
Trichromatic theory: Theory proposing color vision as influenced by three different cones responding preferentially to red, green and blue.
Tympanic membrane: Ear drum, which separates the outer ear from the middle ear.
Tympanic membrane: Thin, stretched membrane in the middle ear that vibrates in response to sound. Also called the eardrum.
Unimodal: Of or pertaining to a single sensory modality.
Unimodal components: The parts of a stimulus relevant to one sensory modality at a time.
Unimodal cortex: A region of the brain devoted to the processing of information from a single sensory modality.
Ventral pathway: Pathway of visual processing. The “what” pathway.
Vergence angle: The angle between the line of sight for the two eyes. Low vergence angles indicate far-viewing objects, whereas large angles indicate viewing of near objects.
Vestibular compensation: Following injury to one side of vestibular receptors or the vestibulocochlear nerve, the central vestibular nuclei neurons gradually recover much of their function through plasticity mechanisms. The recovery is never complete, however, and extreme motion environments can lead to dizziness, nausea, problems with balance, and spatial memory.
Vestibular efferents: Nerve fibers originating from a nucleus in the brainstem that project from the brain to innervate the vestibular receptor hair cells and afferent nerve terminals. Efferents have a modulatory role on their targets, which is not well understood.
Vestibular system: Parts of the inner ear involved in balance.
Vestibular system: Consists of a set of motion and gravity detection receptors in the inner ear, a set of primary nuclei in the brainstem, and a network of pathways carrying motion and gravity signals to many regions of the brain.
Vestibulocochlear nerve: The VIIIth cranial nerve that carries fibers innervating the vestibular receptors and the cochlea.
Vestibulo-ocular reflex: Coordination of motion information with visual information that allows you to maintain your gaze on an object while you move.
Vestibuloocular reflex: Eye movements produced by the vestibular brainstem that are equal in magnitude and opposite in direction to head motion. The VOR functions to maintain visual stability on a point of interest and is nearly perfect for all natural head movements.
Weber’s law: States that just noticeable difference is proportional to the magnitude of the initial stimulus.
What pathway: Pathway of neural processing in the brain that is responsible for your ability to recognize what is around you.
Where-and-How pathway: Pathway of neural processing in the brain that is responsible for you knowing where things are in the world and how to interact with them.