Introduction to sensation and perception

define sensation

define sensation

registering stimulation of the senses

define perception

processing and interpreting sensory info

define cognition

using perceived info to learn/classify/comprehend

define bottom-up processing

perception starts with the physical characteristics of stimuli and basic sensory processes (e.g. feature detectors)

define top-down processing

the perceiver constructs their understanding of external stimuli based on their past experience and knowledge

explain Gibson’s concept of “direct perception”

• info coming from sensory receptors is enough for perception to be rich and detailed (complex mechanisms are not necessary)

• the environment contains sufficient cues to provide context to aid perception

what are the fundamental concepts of sensation and perception?

• change (in the environment)

• different sensory organs (i.e. 5 senses)

• types of receptors (contained in the sensory organs)

• different receiving areas of cortex

what are the types of changes in the environment that can occur?

• electromagnetic energy

• chemical composition

• air pressure waves

• tissue distortion

• graviy/acceleration

what are the receptors in the sensory organs?

• photoreceptors

• chemoreceptors

• mechanoreceptors

• thermoreceptors

what are the cortices involved in sensation and perception?

• primary visual cortex

• gustatory cortex

• olfactory cortex

• auditory cortex

• somatosensory cortex

• temporal cortex

describe the process of sensation and perception in the body and brain

environmental stimulus → sense organ → sensory pathways → brain

what is transduction and where does it occur?

the conversion of environmental energy to nerve signals (in the receptors)

describe staining

apply stains to dead brain tissue which bind to different types of cells or receptors to allow you to see the structure of the brain

describe single-cell recordings (electrophysiology)

insert fine electrodes into the brain (usually of animals) to measure neuron sensitivity to certain stimuli (the action potentials of neurons are recorded with microelectrode inserted close to the cell)

describe an FMRI (functional resonance imaging)

tells you which parts of the brain are active in response to certain stimuli and the interconnections between different parts of the brain

describe lesion studies

studying the deficits of patients with brain damage (example: Phineas Gage)

describe an event-related potential (ERP) from electro-encephalogram (EEG)

records electrical activity across the scalp (especially good at recording the time course)

what is optical imaging/near infra-red spectroscopy (NIRS)?

light sensors sit on the scalp which are powerful enough to go through the skull and reflects off of the brain allowing you to measure the change in reflective light producing a measure of the blood flow over the surface of the brain

describe psychophysics

measuring the psychological response to physical stimuli (manipulate a physical stimulus and measure the psychological response by asking the participant to respond in a certain way)

how can illusions and introspection be used?

useful for understanding perception as when we know what we’re experiencing isn’t real we can begin to question why our brain has constructed things that way for us

describe computational modelling

build a computer that works in a way that you think approximately is how the brain might work and present it with a stimulus - if it responds in a similar way to how people respond you can infer that people work in a similar way to the computer model

describe the findings from Quiroga et al.’s study using single-cell recording

single neurons can be selective for a stimulus as specific as one particular person (selective neurons in medial temporal lobe represent individuals in multiple sensory modalities)

what are the types of lesion studies?

• animal lesioning

  • by knife (also cuts axons)

  • by neurotoxins (only destroys nerve cells)

• neuropsychology

  • damage to brain due to stroke, trauma, road accident etc.

what are the disadvantages of animal lesioning?

• ethical issues

• studying a faulty system

• brain changes in response to damage

what are the disadvantages of neuropsychology?

• damage can be spread out

• individual variation in damage

what is TMS (transcranial magnetic stimulation)?

apply pulses of magnetic energy to the skull/brain to disrupt activity in a small part of the brain for a short period (virtual lesions)

what is absolute/detection threshold (in psychophysics)?

smallest stimulus intensity needed for detection

what is difference threshold?

smallest difference between two stimuli that can be detected - the ‘just-noticeable difference’ (JND)

how does autism in children affect perception of biological motion?

they show poorer performance than typically developing children for biological motion but not for form task

what is bistable perception?

the perceptual phenomenon where an observer perceives the same stimuli (e.g. visual illusions) in two different ways