Chapter 5 Key terms Flashcards
Describe the process of converting sensory input into electrical activity for
hearing, touch, smell, taste, and vision.
For hearing, sound waves travel through the ear and cause hair cells in the cochlea to bend, generating electrical signals sent to the brain via the auditory nerve. For touch,
tactile receptors in the skin convert stimuli into electrical signals that are transmitted to
the brain via sensory pathways. For smell, odor molecules bind to olfactory receptors, which send electrical signals to the brain through the olfactory bulb. For taste, taste
receptors in taste buds detect chemical molecules and convert them into signals sent to the brain via the gustatory nerve. For vision, light stimulates photoreceptors in the retina, which generate electrical signals transmitted to the brain via the optic nerve.
How is spatial information represented in auditory, visual, and tactile domains?
What is topographically organized for each of these domains?
In the auditory domain, spatial information is represented tonotopically, with neurons organized by sound frequency. In the visual domain, retinotopy organizes neurons by their location on the retina. In the tactile domain, somatosensory maps organize neurons by their corresponding skin receptor locations, forming a homunculus in the cortex.
What is meant by hierarchical and parallel processing in the visual system?
Hierarchical processing refers to sequential stages that extract increasingly complex
features, while parallel processing refers to simultaneous processing of different features, such as color, motion, and form. Evidence includes distinct layers in the LGN and specialized V1 neurons for different features.
How does perception differ from sensation?
sensation is the detection and transduction of environmental stimuli into neural signals, while perception is the brain’s interpretation and organization of these signals
into meaningful experiences
MT/hMT is often described as a “motion” area. What are the lines of evidence that
support this idea?
Electrophysiology shows MT neurons are motion-sensitive, and lesions impair motion
perception. Neuroimaging demonstrates increased MT activity during motion tasks, and stimulating MT induces motion sensation.
Similarly, V4 is sometimes described as a “color” area. What is the evidence that
V4 processes color?
Neurons in V4 are color-selective, and damage to V4 impairs color perception.
Additionally, V4 responds to other visual features like orientation, suggesting broader processing roles.
What are the shapes of the receptive fields of retinal ganglion cells, LGN cells, and
V1 simple cells? How might one construct a V1 simple cell receptive field by
wiring together LGN cell receptive fields?
Retinal and LGN cells have circular center-surround receptive fields. V1 simple cells have elongated fields, constructed from the input of multiple LGN cells arranged in a line, creating sensitivity to specific orientations.
What role does cortical magnification play in sensory perception?
Cortical magnification emphasizes processing resources for regions like the fovea or fingertips, improving sensitivity and acuity for these areas compared to others.
How do multisensory integration processes enhance perception?
Multisensory integration combines input from different senses, enhancing accuracy and reaction times, such as combining visual and auditory cues to localize sound sources.
What is the role of saccades in visual perception?
Saccades shift the eye rapidly to focus on different parts of the visual scene, allowing
detailed information to be collected from regions with high acuity, such as the fovea.
Achromatopsia
A condition characterized by a partial or total absence of color vision; they cannot perceive color vision. It is linked to ventral temporal damage. These people have extreme sensitivity to light and poor visual acuity. It is also linked to damage to the V4 of the occipital lobe (ventral medial region). Lesions that produce achromatopsia are relatively large; the pathology tends to encompass V4 and the region anterior to V4. Individuals with this disorder are able to see and recognize objects.
Acuity
How well we can distinguish among stimuli within a sensory modality. Visual acuity is the ability to see fine details, such as the finest line that can be detected. Perceptual acuity is the ability to use observations to make sense of the world and guide an organization through change. Sensory acuity is the ability to use the senses to perceive stimuli and make accurate observations. Our acuity is best in the center of the visual field, b/c the central region of the retina, the fovea, is packed with photoreceptors.
What factors does acuity depend on?
- the design of the stimulus collection system.
- the number and distribution of the receptors.
Adaptation
Perception adaption is the process of adjusting how we perceive stimuli over time. Sensory adaption includes reducing responsiveness to constant stimulation, allowing focus on changes in input. Adaption is the adjustment of the sensory system’s sensitivity to the current environment and to important environmental changes.
Akinetopsia
A rare brain disorder that impairs a person’s ability to perceive motion; motion blindness. It is associated with damage to the visual cortex, specifically the lateral occipital-temporal (MT/V5 area).
Auditory cortex
The most highly organized processing unit of sound in the brain. It is located on the superior temporal gyrus in the temporal lobe. Neurons in the auditory cortex have frequency-dependent receptive fields. Damage to the higher-order auditory cortex can affect voice recognition and discerning what is being heard. Damage to the primary auditory cortex can affect sound localization.
Auditory pathway
in the central nervous system that transmits and processes sound signals from the ear to the cortex.
E ar recepter cells (haircells); located within the organ of corti inside the cochlea of inner ear. These cells are responsible for converting sound vibrations into electrical signals.
C ochlear nucleus; the first structure in the brain structure in the brain’s auditory pathway, where the auditory nerve enters the brainstem. It is responsible for processing sound info from the inner ear.
superior O live; where it becomes binaural, role in sound localization.
Lateral lemiscus; bundle of axons in the brainstem that carries sound info from the cochlea to the inferior colliculus.
Inferior colliculus; structure in the midbrain that relays auditory info from the inner ear to the brain’s auditory cortex, it processes sound waves into electrical signals that travel to the brain.
M gn (medial geniculate nucleus); the role is passing auditory info from the inferior colliculus to the auditory cortex.
A uditory cortex
Blind spot
The small circular area at the back of the retina where the optic nerve enters the eyeball and which lacks photoreceptors (rods and cones) and is not sensitive to light (no light-sensitive cells). This exists because the optic nerve exits the retina at a specific point, creating a small area where there are no light-sensitive cells, meaning that the spot cannot detect light and, therefore, cannot produce a visual image.
center-surround organization
center-surround receptive fields emphasize edges (differences in light levels). Ganglion cells maintain a center-surround organization. Cells in the LGN have concentric receptive fields with either an on-center, off-surround organization or an off-center, on-surround organization. The on-center, off-surround cell fires rapidly when the light encompasses the center region and is inhibited when the light is positioned over the surround. A stimulus that spans both the center and the surround produces little change in activity.
Chemical senses
Gustation (taste) and smell (olfaction); these senses interpret the environment by dsicriminating between different chemicals. They both begin with a chemical stimulus. They both rely on detecting chemical molecules in the environment to send signals to the brain for interpretation as a sensory experience.
Color vision
Loss of color vision results in achromatopsia. Color vision is enabled by cone receptors. The ability to see and differentiate colors.
1. Light enters the eye and stimulates different types of cones
2. the cones send signals to the brain via the optic nerve
3. the brain processes the signals from the cones to perceive color.
Columnar organization of sensory cortex
the arrangement of neurons in the sensory areas of the brain into vertical columns, where each column contains a group of neurons with similar properties, like responding to the same type of sensory input from a specific area of the body. V1 has a columnar organization for ocular dominance and orientation tuning
Cone
Each cone connects to an individual output cell, press and provides high acuity. Cones enable color vision via 3 types that respond to different light frequencies. It has 10-100x less sensitive than rods and functions best in bright environments.
Cortical magnification
Certain sensory regions (eg. fovea or fingertips) are represented by disproportionately larger cortical areas, it enhances resolution and discrimination in highly sensitive regions, enabling more detailed perception and precise interpretation of stimuli. It describes how the brain allocates neurons to process visual and tactile info.
Dorsal streams
a visual pathway in the brain that helps you visually locate objects and guide your actions; the where/how pathway. The dorsal stream starts in the primary visual cortex in the occipital lobe, and continues along the dorsal surface of the brain to the parietal cortex. It helps you process visual info to construct representations of objects you want to manipulate. The “where” pathway’s tuning allows for precise motion interpretation, supporting navigation and understanding of dynamic environments. The “how” pathway is a visual system that helps you perceive where objects are in space and how to interact with them.
Ventral streams
The ventral stream plays a key role in color perception, crucial for object recognition and detailed visual analysis. The visual pathway specializes in object identification, face recognition, and fine detail perception, determining what we see. A pathway that carries visual info from the primary visual cortex to the temporal lobe. It begins in the primary visual cortex, runs along the bottom surface of the brain. It ends in the inferior temporal cortex (IT). It connects with the medial temporal lobe, limbic system, and dorsal stream.
Extrastriate
Extrastriate visual areas are a subdivision of cortical visual areas that lie outside the striate cortex and are considered secondary visual areas b/c they receive input either directly or indirectly from the primary visual cortex. Damage to the extrastriate cortex causes achromatopsia. It is a brain region central to mental representations of motion. It illustrates hierarchal processing, where higher-level areas synthesize lower-level areas synthesize lower-level inputs to construct complex visual features.
Fixation point
a specific place on the retina or on a screen where the eye are focused; the point in the visual field that is fixated by the 2 eyes in normal vision and for each eye is the point that directly stimulates the fovea of the retina. Saccades are the rapid eye movements that happen ~3-4 times a second in order to focus on different parts of the visual scene.
Fovea
Foveal stimuli have the highest acuity, essential for object vision. The central region of the retina that is densely packed with cone cells and provides high-resolution visual info. The fovea is represented by disproportionately larger cortical areas. It’s a small depression within the retina where visual acuity is the highest.
Functional specialization
A theory which suggests that different areas in the brain are specialized for different functions. Ex. Dorsal/ventral pathway, pattern/component cells.
Gustation
The action of tasting. Primary gustatory afferent neurons relay taste signals from taste cells to the brainstem. The gustatory pathway: primary gustatory afferent neurons relay taste signals from taste cells to the brainstem. Signals proceed to the thalamus, then the primary gustatory cortex (frontal operculum), and finally to the insula (secondary taste areas). Damage to the primary gustatory cortex results in impaired taste perception, whereas damage to the insula affects food recognition and flavor intensity. In the gustatory pathway, each afferent fiber connects to multiple taste buds with various taste cells.
Homunculus
The body map in S1 (primary somatosensory cortex) the reflects receptor density and sensory importance, not physical size. The primary somatosensory cortex (S1) contains a homunculus of the body, wherein the more sensitive regions encompass relatively larger areas of cortex.
Lateral Geniculate Nucleus (LGN)
a relay station in the thalamus that plays a crucial role in visual processing, it is located in the posterior portion of the thalamus, on either side of the midline. LGN neurons project to V1, where multiple inputs converge onto single V1 neurons, enabling spatial summation and the development of orientation-selective receptive fields. The right LGN receives input from the left visual field. The left LGN receives from the right visual field. LGN replays info to the primary visual cortex (V1) in the posterior occipital cortex. It has 6 layers.
Magnocellular Layer
It provides useful static, depth, and motion info. It contains large receptive cells that receive their input from the large M-type retinal ganglion cells. M-cells in the magnocellular pathway have a transient response and they respond to coarse detail, and motion.
Mechanoreception
The process by which organisms detect and respond to mechanical stimuli, such as touch, pressure, vibration, and acceleration. It converts sound waves into neural signals (auditory). Touch uses mechanoreception to detect pressure, temperature, stretching, and vibration. Hearing uses mechanoreception to detect vibration as hearing (hair cells).
Motion aftereffect
A visual illusion that makes stationary objects appear to move in the opposite direction to a moving object you’ve recently viewed; caused by prior exposure to motion in the opposite direction. The visual system adapts to the motion of a moving object. When one fixates on a stationary object, the adapted cells cause the stationary object to appear to move.
MT/hMT
Middle/medial temporal area that processes complex motion stimuli, such as plaid patterns. MT supports the “where” pathway for motion processing. MT neurons are finely tuned to direction and speed, enabling detection of object trajectories and velocities. It’s located in the dorsal pathway of the brain, on the border of the occipital, temporal, and parietal lobes.
Nociceptor
(free nerve endings) the somatosensory receptors that convey pain info. Nociceptors are activated when the temperature reaches a level that could cause tissue damage. They trigger pain sensations when activated by extreme stimuli.
Ocular dominance columns
Stripes of neurons in the primary visual cortex (V1) of the brain that preferentially respond to input from one eye or the other. The columns span multiple cortical layers and are laid out in a striped pattern across the striate cortex (V1). In the primary visual cortex, cells with the same eye preference are grouped into ocular dominance columns.
Olfaction
The sense of smell, it’s a chemical sense. The primary olfactory cortex receives input from the bulb. The olfactory pathway relays signals to the hippocampus, amygdala, and indirectly to the reticular formation and hypothalamus. It bypasses the thalamus, connecting directly to the cortex; enabling direct influence on brain areas involved in memory and emotion. Signal transduction of odors begins when the odorant attaches to receptors in the olfactory epithelium. The signal is then sent to the olfactory bulb through the olfactory nerve, which projects to the primary olfactory cortex. Signals are so relayed to the orbitofrontal cortex, a secondary olfactory processing area.
Orientation tuning
A property of neurons in the visual cortex that allows them to respond to the orientation of a visual stimulus. A measure of how a cell’s firing rate depends on the orientation of a stimulus. V1 neurons use orientation tuning by selectively responding to visual stimuli with specific orientations, meaning each neuron fires most strongly when presented with a line or edge at a particular angle, allowing the brain to extract info about the orientation of objects in the visual field, forming a detailed representation of the visual scene based on the combined activity of many orientation-tuned neurons across the V1 cortex.
Parvocellular layer
Have a small receptive field and so represent the visual image with high resolution. The outer 4 layers of the LGN are parvocellular layers. It contains p-cells (parvocellular cells); parvocellular layers are crucial for fine details and color vision.
P-cell
receives input from midget ganglion cells in the retina, apart of the parvocellular pathway. These cells have a sustained response and responds to fine detail, color. Small receptive fields.
Perception
Interpretation of sensations by the brain: the process of selecting, organizing, and interpreting sensory info to create meaningful experiences. Higher-level mental processes guide further construction of perceptions.
Photoreceptor
The sense receptor for vision; cones and rods. Specialized cells in the retina that transduce light energy into changes in membrane potential. The photoreceptors are the interface for the visual system between the external world and nervous system. The human eye has 2 types: rods and cones.
Proprioception
the awareness of the body position and movement. The senses that fall under proprioception include: joint position sense, kinesthesia, sense of force, sense of change of velocity. The awareness of the position of one’s own body parts, such as limbs. This awareness arises from the info provided by specialized nerve cells at the linkage of the muscles and tendons.
Receptive field
the area of the body/ visual field where a stimulus can affect a sensory neuron. The area of stimulus space over which changes in the stimulus cause corresponding increases or decreases in the firing rate of the neuron. Small receptive fields are stimulated by high spatial frequencies and fine detail; large receptive fields are stimulated by low spatial frequencies and coarse detail. Receptive field size increases further along the hierarchy, allowing for broader integration of visual info.
Retina
Has 2 types of ganglion cells: m and p-cells. It is located at the back of the eye and converts light into electrical signals that are transmitted to the brain for visual interpretation. Visual info travels from the retina through the optic nerve to the thalamus. It includes photoreceptors and ganglion cells.
Retinal ganglion cell
They are the primary neurons in the retina responsible for converting light signals into electrical impulses that are transmitted to the brain for visual perception; they collect all the visual info perceived by the eyes and send it to the brain where it will be processed. Each retinal ganglion cell responds to stimulation in a specific area of visual space.
Retinotopy
Systematic representations of visual space across the cortical surface. Neighboring neurons along the cortical surface receive input from adjacent parts of the retina, representing adjacent parts of visual space. The process of organizing visual info from the retina onto neurons in the brain; the mapping of visual input from the retina to neurons, particularly those neurons within the visual stream.
Rod
More numerous in humans and sensitive to dim light. Detects variations in light intensity. Many rods converge onto a single output cell, reducing spatial precision. Photoreceptors that have a lower threshold for light stimuli than cones have, and thus enable vision in low-light conditions. Rods are found in the periphery of the retina and not in the fovea. Many rods connect to one ganglion cell.
Saccades
The rapid eye movements that are made to change fixation from one point to another. A saccade lasts 20 to 100ms. Occurs when jumping between fixation points.
Scotoma
A partial loss of vision or blind spot in an otherwise normal visual field. It occurs due to a number of possible reasons, including brain/eye issues, injuries, and medications, or retina/brain damage. Results from damage to the optic nerve, retina, or visual cortex in the brain.
Selectivity
The ability of a legend to bind to a receptor and induce specific cellular responses, influencing signaling and receptor endocytosis. Neuronal selectivity refers to a neuron that responds preferentially to specific stimuli based on the attentional template formed by the brain. Direction-selective neurons give larger responses to motion in the preferred direction versus motion in the opposition, null direction.
Sensation
The detection and conversion of physical energy (stimulus) from the environment into neural signals, forming the foundation for perception. Detection of physical energy and transduction, the conversion into neural signals.
Somatosensory cortex
(aka S1) The initial cortical processing area for somatosensation. This area of the brain contains a somatotopic representation of the body called the sensory homunculus. It is responsible for processing and interpreting sensory info from the skin, muscles, joints, and tendons. It plays a role in perceiving touch, temperature, pain, proprioception…etc.
Spatial frequency map
Shows how spatial frequencies are represented in the visual cortex; spatial frequency refers to the number of pairs of bars that can be imaged within a given distance on the retina. Adjacent regions respond to closely related frequencies, forming a spatial frequency map. Neurons in the primary visual cortex (V1) respond preferentially to stimuli with distinct orientations and spatial frequencies.
Taste bud
Where taste cell cluster into; are sensory organs that allow you to taste and perceive the chemical composition of food and drink. They are located on the tongue and other parts of the mouth. They contain sensory cells that are connected to nerve fibers.
Tonotopic maps
It deconstructs complex sounds into simpler frequency components for detailed processing. A mapping of different frequencies onto the hair cells along the cochlear canal and also the auditory cortex, with neighboring frequencies represented in neighboring spatial locations
Topographic maps
It projects a sensory surface or effector to the central nervous system; the topographic organization of the audition is a sound frequency map (tonotopy). The topographic organization of tactile (touch) is a body map (homunculus). The topographic organization of vision is a visual field map (retinotopy).
V1 complex cell
Cells that integrate inputs from multiple simple cells; They respond to more advanced visual features, such as motion and texture orientation; refines the processing hierarchy, supporting higher-level visual analysis. They are layers IV, ii/iii. It responds to both bars of light and dark, motion and orientation selective.
V1 simple cell
Cells in the V1 that emerge from this convergence and respond selectively to specific orientations. They are located in layer IV, they prefer bars of light/bars of dark. They are orientation-selective.
Visual field
The visual field is inverted across the retina, a common feature in all vertebrates. Each hemisphere processes the contralateral visual field; it uses retinotopic organization. The visual field of each eye is divided into left and right halves. Damage results in a loss of vision in a specific part of a person’s peripheral vision, caused by damage to the optic pathway in the brain.
Visual processing
The complex series of steps that the brain takes to convert light info into a meaningful visual image. The visual pathway:
1) visual info travels from the retina through the optic nerve to the thalamus.
2) most retinal input is sent to the LGN; some projections reach the superior colliculus via the pulvar.
3) nasal optic nerves from each eye cross at the optic chiasm.
4) the LGN relays visual info to the primary visual cortex (V1) in the posterior occipital cortex.
