From Signals to sensations Flashcards
what are the senses?
SYNAPSES The senses convey specific information about some source of physical energy
Each sensory modality has a “labelled line”
Each sensory modality has specialised receptors for transduction
e.g. the pancian corpuscle
Pit Vipers and thermoreception
Can sense temperature changes as little as 0.002 degC
hearing freqiencies
elephants hear lower freq than humans and cats hear higher
what are the codes of a sensory modality?
Intensity coding
Location coding
Coding for specific object properties (colors, shapes, pitch)
what is a stmilulus and what is a sensory receptor organ?
Sensory Receptor Organs act as filters of the environment: they detect and respond to some events and not others
Stimulus event that affects the sensory organ
what are the principles of sensory coding?
Sensory systems appear to be very diverse
Yet they all solve the same task:
They convert environmental signals into neural activity that can influence the motor system of the animal
Methods for studying sensory processing:
- Psychophysics:behavioral testing to establish the sensitivity of a sensory system and the “rules” of its operation.
- Electrophysiological recording: from single neuron or small groups of neurons along the sensory pathway to find out how the neural circuitry gives rise to the perceptual abilities. 3. Neuroimaging in humans: perceptual tasks to identify the brain areas responsible.
what must be sensed?
Qualitative features such as colour or odorant à often referred to as modality- what is it?
• Quantitative features such as magnitude à often referred to as the intensity of a stimulus
• Temporal features such as duration or frequency of a signal à often referred to as the duration of a stimulus
• Spatial location of a stimulus
where is it?
Typically, all these aspects are estimated at once: a common strategy of sensory systems is to have separate neural pathways specialized for estimating different types ofstimulus features.
Visual system analyzes colour, shape and movement in different brain regions.
what are the areas of the occipital cortex?
V1: segregates pattern vision from motion signals
V2: 3D vision, seeing camouflage, more complex patterns
V3: shape perception
V4: colour area and shape perception
V5: motion area
what are the 2 main functions of each sensory system?
Detection
The detection of a signal.
Weak signals can be detected without the animal being able to finely discriminate any of its features.
Discrimination
Discrimination of some aspects of a sensory input.
This is often referred to as estimation
what is an adequate stimulus?
type of stimulus for which a given sensory organ is particularly adapted
Transducer function of receptors the process in which a stimulus energy is transduced into the electrical response
stimulus –> electrical responce –> Brain
what is sensory processing?
Sensory processingstartswithreceptorcells • A give receptor cell is specialized to detect particular energies or chemicals • Upon exposure to the stimulus, a receptor cell converts that energy intoachangeinelectricalpotentialsacrossitsmembrane • Changing thesignal àSENSORYTRANSDUCTION
how is a stimuli transduced?
The structure of the receptor determines the form of energy to which it will respond
Receptor Potential
step between the arrival of energy at receptor cell and the initiation of an action potential It is usually an EPSP
outline transductino of mechanical signals
Excitatory events:
- mechanical stimulation deforms the corpuscle
- deformation of the corpuscle stretches the tip of the axon
- stretching the axon opens mechanically gated ion channels in the membrane, allowing sodium ions to enter
- when the receptor potential reaches the threshold amplitude, the axon produces an action potential
what are the 4 stages of sensing something
Sensory transduction They transduce [transform/translate] the energy of a stimulus into a change in membrane potential
- Amplification They strengthen the energy of the stimulus The action potential conducted from the eye to the brain contains 100,000 times more energy than the few photons of light that stimulated the receptor
- Transmission Action potentials from receptors, or from neurons connected to receptors, reach the CNS
- Integration Receptors contribute to the processing of a signal. For example many receptors show sensory adaptation. This term means that they respond less during continued stimulation
explain modality as a attribute of the sesnes
The most basic mechanism for identifying the nature of a sensory input is via labeled lines
Input from the optic nerve is always interpreted by the brain as visual input
The connections of “pain” and “touch” fibers in the somatosensory system are entirely different àstimulation of either leads to the appropriate sensation
Much finer discriminations
how are receptors different based on what system they#re part of?
auditory and visual systems: a distinct type of receptor cell is present. In the auditory system, the receptor synapses directly on the ganglion cell, whereas in the visual system, an interneuron receives synapses from the photoreceptor and in turn synapses on the retinal ganglion cell.
somatosensory system: receptor is a specialized peripheral element that is associated with the peripheral process of a sensory neuron
What is the labeled line concept?
Messages from different senses use the same type of energy:
Action Potentials
Labeled Lines
particular neurons are at the outset labelled for distinctive sensory experience
The brain recognises the different sensations as separate and distinct:
each sensory modality sends its action potentials along separate nerve tracts
