Week Nine - Sensation & Perception Flashcards
What is Sensation?
The manner in which our sense organs receive information from the environment
What is Perception?
The manner by which people select, organise, and interpret sensations
- understanding a stimulus
What is Transduction?
The manner by which physical energy is converted into sensory neural impulses
What is the former sensory system organisation?
receptors > thalamus > primary sensory cortex > secondary sensory cortex > association cortex
COMPLETELY BOTTOM-UP APPROACH
What is the neocortex?
A thin sheet of cells covering the rest of the brain
How are cells organised in the neocortex?
Into 6 stereotypical layers.
The types of cells, their spatial arrangement and connections are pretty much the same in every part of the neocortex
What is the sensory organ and receptors for vision?
The eye
Rods and Cones
They transduce neural signals up the optic nerve
Explain the process in the primary visual pathway
retina - optic nerve - optic chiasm - thalamus - occipital lobe
Explain the process in the primary auditory pathway
auditory nerve - cochlear nuclei - superior olivary nuclei - inferior colliculus - medial geniculate - auditory cortex
What is the thalamus?
The gateway to the cortex (relay station)
What doesn’t pass through the thalamus?
Olfaction
What is a Multisensory Integration area?
The area in which information is assimilated from various individual sensory systems and coordinated
How does hearing occur?
It occurs via sound waves, which result from rapid changes in air pressure caused by vibrating objects
What is pitch? (amplitude)
Frequency of vibration measures in hertz
What is Loudness? (frequency)
Function of sound wave intensity
What does timbre do? (complexity)
Provides information about the nature or complexity of the sound
Where are primary auditory receptors located? What are they?
In the cochlea (inner ear)
They are tiny hair cells that convert sound energy to neural impulses and send them along to the primary auditory cortex
What is the route of transduction of auditory information?
cochlea > superior olives > colliculi > thalamus > primary auditory cortex
What is the external ear called?
The pinna
What is the name of the eardrum?
Tympanic membrane
What is the middle ear?
A hollow region between the eardrum and the cochlea, containing the ossicles
What are ossicles?
The middle ear bones (these vibrate from sound waves and transmit it to the inner ear)
- malleus
- incus
- stapes
What is the Cochlea?
A snail-shaped structure of the inner ear containing the organ of corti
What is the Organ of Corti?
A sensory organ for the auditory system (the eye basically)
- basilar membrane
- hair cells
- tectorial membrane
What does the stimulation of hair cells trigger?
Action potentials in the auditory nerve
What does the basilar membrane consist of?
A base and an apex
What do natural, low-frequency and high-frequency sounds do in the basilar membrane?
natural = excite cells across the membrane low = excite cells near the apex high = excite cells near the base
What is the general process of how sound waves get in?
They vibrate the eardrum, which causes reactions in the bones then affecting the oval window, fluid moves around causing hair cells to bend in different ways depending on the soundwave
What is the secondary auditory cortex?
The superior temporal gyrus
Auditory signals are conducted to what two areas of the association cortex?
Prefrontal cortex
Posterior parietal cortex
What and Where pathway
Anterior Auditory Pathway more involved in identifying sounds (what) (front)
Posterior Auditory Pathway more involved in locating sounds (where) (back)
What are Odorants?
Molecules that give off a smell (they bind to receptors in olfactory cilia)
What are Glomerculi?
Clusters of convergent olfactory sensory neurons
What is taste referred to as?
Gustation
Where are taste receptors located?
Tongue and oral cavities in clusters of about 50
What are the 4 primary tastes
sweet, sour, salty, bitter
What is the 5th taste?
Umami (meat or savoury)
Explain the receptor information about salty and sour taste?
salty and sour do not have receptors, they merely just act on ion channels
What is the process of gustation?
receptors (papillae) > solitary tract > thalamus > cortex
What is the Somatosensory system composed of?
Three separate and interacting systems
Exteroceptive - external stimuli (touch, pressure, pain)
Proprioceptive - body position
Interoceptive - internal body conditions (eg temperature, blood pressure)
What do Merkel’s Disks do?
Detect regular touch
Meissner’s corpuscles?
Detect light touch
Pacinian corpuscles?
Detect Deep pressure (gradual skin indentation)
Ruffini corpuscles?
Detect temperature on the skin
Nociceptors?
Detect pain
What are the 2 major pathways in the Somatosensory system?
Dorsal-column medial-lemniscus system: Mainly touch and proprioception
Anterolateral System: Mainly pain and temperature
What does the iris do?
Controls how much light enters the eye
What is the pupil?
A hole where the light enters the eye
What does the retina do?
Receives light that the lens has focussed and converts it into neural signals for the brain
What does the optic nerve do?
Travels from the retina to the brain
What is the fovea?
It is the central part of our eye responsible for acuity (sharpness of vision) and this is why we move our eyes
What is the ‘blindspot’
A region of the retina that contains no rods or cones - therefore nothing to detect vision
Where are our sensory receptors in the eye?
At the back - moves along the cells to the front of the eye via the optic nerve
What are cones?
Photopic (daytime) vision. High acuity colour information in good lighting. Only found at the fovea
What are rods?
Scotopic (night time) vision.
High sensitivity, allowing for low-acuity vision in dim light but lacks detail and colour
Difference between ganglion cells for each cone and rod?
Cone = 1:1 Rods = many rods for each ganglion cell
How does vision reach the primary visual cortex?
Travels on optic nerve > reaches optic chiasm > crosses over to lateral geniculate (thalamus) > goes to primary visual cortex
Explain the flow of visual information
Thalamic relay neurons > visual cortex (striate) > visual cortex (prestriate) > visual association cortex
What happens to receptive fields as visual flows through the hierarchy?
They become larger and respond to more complex and specific stimuli
What kind of cells do receptive fields have?
Simple cortical cells
Complex cortical cells
Which part of the brain gets sensory input from all systems?
The superior colliculus
What is found with those with Synesthesia?
Stronger white matter connectivity - more axons between sensory areas
What is total deafness in humans caused by?
- Conductive deafness (damage to ossicles)
2. Nerve deafness (damage to cochlea)
What does parietal cochlea damage result in?
Loss of hearing at particular frequencies
What is Anosmia?
Inability to smell
Commonly caused by a blow to the head that damages olfactory nerves
What is Ageusia?
Inability to taste (not common at all)
What is Astereognosia?
Inability to recognise objects by touch
What is Asomatognosia?
The failure to recognize parts of one’s own body
What is a loss of colour vision called?
Achromatopsia - caused by bilateral damage to the occipital lobe in V4
What is Akinetopsia?
Selective loss of motion perception (eg cant see moving cars)
What is Scotomas?
Discrete regions of blindness
What is neglect syndrome?
Involuntary failure to attend to sensory stimuli presented in the side of space opposite to the site of brain injury (eg only shaving one side of your face)
