General Principles of Sensory Processing PDF

Chapter 8: General Principles of Sensory Processing, Touch, and Pain General Principles of Sensory Processing - The Five Senses? - Stimulus Salience - Sensation and Perception - The Law of Specific Nerve Energies - Sensory Receptors - 3 Stages of Sensation...

Chapter 8: General Principles of Sensory Processing, Touch, and Pain General Principles of Sensory Processing - The Five Senses? - Stimulus Salience - Sensation and Perception - The Law of Specific Nerve Energies - Sensory Receptors - 3 Stages of Sensation - Organization of Sensory Processing - Processing of Stimulus Intensity/Frequency - Adaptation to a Stimulus - Plasticity in Sensory Processing Somatosensation - Epicritic Touch - Protopathic Touch 1 General Principles of Sensory Processing 5 Senses. ??? - vision (sight) - audition (hearing) - somatosensory (touch) - gustatory (taste) - olfactory (smell) - each sensory system processes multiple attributes of a stimulus - individual sensory systems have multiple types of sensory receptors and distinct hierarchical neural pathways that extract and integrate stimulus features 2 2 General Principles of Sensory Processing 5 Senses. ??? - vision (sight) - audition (hearing) - somatosensory (touch) - pressure - gustatory (taste) - temperature - olfactory (smell) - pain - vestibular (balance) - proprioception - each sensory system processes multiple attributes of a stimulus - individual sensory systems have multiple types of sensory receptors and distinct hierarchical neural pathways that extract and integrate stimulus features 3 3  General Principles of Sensory Processing Stimulus Salience. umwelt = species specific perceptual world, differs between species - social odour recognition in most mammals, but not humans - salience is a consequence of brain processing important modalities occupy relatively larger brain regions 4 4 General Principles of Sensory Processing Sensation and Perception. - sensation = detection of stimulus and recognition that event has occurred - constructed differently among differing species - perception = interpretation and appreciation of sensory stimulus 5 5 General Principles of Sensory Processing Sensation and Perception. - sensation = detection of stimulus and recognition that event has occurred - constructed differently among differing species - perception = interpretation and appreciation of sensory stimulus 6 6  General Principles of Sensory Processing Sensation and Perception. - sensation = detection of stimulus and recognition that event has occurred - constructed differently among differing species - perception = interpretation and appreciation of sensory stimulus 7 7 General Principles of Sensory Processing Sensation and Perception. - sensation = detection of stimulus and recognition that event has occurred - constructed differently among differing species - perception = interpretation and appreciation of sensory stimulus 8 8 General Principles of Sensory Processing Sensation and Perception. - sensation = detection of stimulus and recognition that event has occurred - constructed differently among differing species - perception = interpretation and appreciation of sensory stimulus 9 9  General Principles of Sensory Processing Johannes Muller – “The Doctrine of Specific Nerve Energies”. - hypothesized that each sensory input to the brain used different nerve “energy”, which the brain interpreted so specific perceptions result - concluded that the brain is functionally divided, and that specific nerves convey specific types of information (auditory, visual, etc.) - all sensory information is eventually encoded as action potentials in “labelled lines” - sensations depend upon which neurons are active, and how active each of those neurons is at a given time 10 10 General Principles of Sensory Processing Sensory Receptors. - specialized neurons that detect specific physical stimuli - note: do not confuse with protein molecules that serve as receptors for neurotransmitters, hormones, etc. - most sensory receptors do not have axons; cell bodies synapse on dendrites or cell bodies of other neurons Pacinian auditory hair corpuscle cell (hearing) (touch) nociceptor (pain, heat) photoreceptors (vision) 11 11 General Principles of Sensory Processing 3 Stages of Sensation. Reception (stimulus to receptor): - absorption of physical energy by sensory receptor Transduction (receptor to neuron): - conversion of physical energy to electrochemical pattern in neurons Coding (neuron to brain): - correspondence between some aspect of physical stimulus and action potentials 12 12  General Principles of Sensory Processing Organization of Sensory Inputs. - all sensory systems are topographically organized. 13 13 General Principles of Sensory Processing Organization of Sensory Inputs. - receptive fields help to sharpen and define sensory inputs - generally, larger receptive fields in less sensitive systems, and smaller receptive fields in more sensitive systems - stimulus localization, movement, and direction of movement can be processed by comparing the inputs of multiple receptive field inputs, limited by the spatial organization of these inputs 14 14 General Principles of Sensory Processing Organization of Sensory Inputs. - lateral inhibition sharpens the acuity of sensory recognition lateral inhibition 15 15  General Principles of Sensory Processing Organization of Sensory Inputs. - successive levels of processing extract more and more complex attributes of stimulus properties, known as hierarchical processing - most sensory information is relayed through thalamus to appropriate cortical circuits } } } } } } } } } } } } } } } } } } } } } } } } } } } } 16 16 General Principles of Sensory Processing Processing of Stimulus Intensity. - intensity may be encoded by which neurons are active - intensity may be encoded by the number of A.P.s in neurons - limited by the limited frequency of firing of a neuron - hearing and vision, more differences in intensity can be discriminated than can be accounted for by the range of firing frequencies of the specific neurons that process this information - assemblies of neurons can act together where different neurons are recruited by higher intensities, so intensity is partly encoded by the number of active cells - assemblies of neurons can fractionate the range of intensity into smaller ranges that are encoded by specialized neurons 17 17 General Principles of Sensory Processing Processing of Stimulus Frequency. - frequency may be encoded by which neurons are active - frequency may be encoded by the number of A.P.s in specific neurons - limited by the limited frequency of firing of a neuron 18 18  General Principles of Sensory Processing Adaptation to a Stimulus. - tonic receptors show slow or no adaptation to a stimulus - phasic receptors undergo rapid adaptation - thus neural activity and perception shift from accurate stimulus representation - stimulus environment ≠ sensation ≠ perception - achieved at level of sensory receptor and/or higher levels of processing - sensory systems may also regulate descending inputs to regulate functions of receptors and early stages of processing (e.g. opioid analgesia) 19 19 General Principles of Sensory Processing Plasticity in Sensory Processing. - experience-dependent plasticity studied in topographical organization of somatosensory maps - peripheral lesions or specific forms of stimulation - monkeys trained to grasp spinning disk at the edge of reach for food reward - disk was far enough from cage so monkey could only grasp with distal segment of digits 2, 3, and sometimes 4 - after 20 wks training, 1.5 hrs per day, cortical representation of somatosensory input from hand reorganized with greater representation of distal aspects of digits 2, 3, and to lesser degree, 4 20 20 Somatosensation Epicritic Touch and Kinesthesia Protopathic Touch - mechanoreceptors for fine and - nondiscriminating, pain and temperature discriminative touch - proprioception dorsal column medial lemniscal pathway spinothalamic pathway 21 21  Somatosensation Epicritic Touch and Kinesthesia. - Pacinian corpuscle: sudden, deep pressure - Meissner corpuscle: sudden, light touch - Ruffini corpuscle: gradual, stretch - Merkel’s Disk: gradual, light touch - proprioceptors (muscle spindles, GTOs, joint proprioceptors) dorsal column medial lemniscal pathway 22 22 Somatosensation Epicritic Touch and Kinesthesia. - Pacinian corpuscle: sudden, deep pressure - Meissner corpuscle: sudden, light touch - Ruffini corpuscle: gradual, stretch - Merkel’s Disk: gradual, light touch - proprioceptors (muscle spindles, GTOs, joint proprioceptors) type IV type III type I and II dorsal column medial lemniscal pathway 23 23 Somatosensation Protopathic Touch, Temperature and Pain. - free nerve endings: responsive to tissue damage, release of intracellular K+ from nerve itself, bradykinins, histamine, etc. due to damage to surrounding tissue - transmit using Aα, Aδ, and C fibers spinothalamic pathway 24 24  Somatosensation Protopathic Touch, Temperature and Pain. - ascending pain fibers release substance P (and others) - analgesia mediated by descending projections from PAG, raphe etc. - descending analgesic action mimicked by opiate drugs - pain may also sensitize (inflammation, neuralgia) 25 25