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Human Physiology · Nervous system and exercise

Special Senses and Higher Functions

Vision, hearing, taste and smell connect us to the world, and the cortex turns sensation into memory, language and decisions. This page explains the special senses and higher functions most relevant to rehabilitation, and how exercise benefits the brain.

9Sections
5Figures
3Tables
10Questions

Part 9 · Nervous System and Exercise · Chapter 46 of 47

Learning objectives

By the end of this page you should be able to:

  • Outline the receptors and pathways of the special senses.
  • Explain visual field defects from lesions of the visual pathway.
  • Describe the physiology of hearing.
  • Describe cortical localisation of language, memory and attention.
  • Explain sleep, learning and memory at a basic level.
  • Summarise evidence on exercise and brain health.

Why it matters

Sensory and cognitive problems change how patients understand instructions, stay safe and learn new skills. Stroke, brain injury and dementia often affect these functions.

Exercise also benefits the brain, giving physiotherapists a role in cognitive health.

The special senses

Figure 1 · The special senses

Five special senses with their receptors and cortical targets Vision uses rods and cones and the occipital cortex; hearing uses cochlear hair cells and the temporal cortex; balance uses vestibular hair cells; taste uses taste buds for five qualities; smell uses olfactory receptors with direct links to limbic areas. Visionrods and cones in retina;occipital cortexHearingcochlear hair cells;temporal cortexBalancevestibular hair cells;see Chapter 44Tastetaste buds: sweet, salt,sour, bitter, umamiSmellolfactory receptors;direct to limbic areasAll transduce a physical or chemical stimulus into receptor potentials, then action potentials
Special senses guide movement. Vision and hearing loss raise falls risk and change how patients learn exercises.
FeatureRodsCones
SensitivityHigh; dim lightLower; bright light
ColourNoYes, three types
LocationPeripheral retinaConcentrated in the fovea
AcuityLowHigh

Figure 2 · Visual pathway lesions

Visual pathway with lesion sites and resulting visual field defects Fibres from the nasal half of each retina cross at the optic chiasm. A lesion of one optic nerve blinds that eye. A chiasmal lesion causes loss of both temporal fields. A lesion of the optic tract or radiation behind the chiasm causes loss of the same half-field in both eyes, a homonymous hemianopia. left eyeright eyeoccipital cortexABCchiasm: nasalfibres crossA: left optic nerve, left eye blindB: chiasm, bitemporal hemianopiaC: right tract or radiation, left homonymousFields shown asseen by thepatient; black =lost
Homonymous hemianopia is common after stroke. Teach scanning towards the blind side and arrange the environment to help. Schematic.

Sound waves move the eardrum and ossicles, which push fluid in the cochlea. Hair cells along the basilar membrane respond to different frequencies, high at the base and low at the apex.

Conductive hearing loss affects the outer or middle ear; sensorineural loss affects the cochlea or nerve.

Higher functions

Figure 3 · Higher functions and the cortex

Main functions of the cortical lobes and deficits after damage The frontal lobe supports planning, judgement, movement and speech output; damage causes apathy, disinhibition, weakness and non-fluent aphasia. The parietal lobe supports sensation and spatial attention; damage causes sensory loss and neglect. The temporal lobe supports hearing, memory and comprehension. The occipital lobe supports vision. Frontalplanning, judgement, motor,speech output (Broca)If damaged:lack of initiative, disinhibition,weakness, non-fluent aphasiaParietalbody sensation, spatialawareness, attentionIf damaged:sensory loss, neglect (oftenleft side after right damage)Temporalhearing, memory,language comprehensionIf damaged:memory loss, fluentaphasia (Wernicke)OccipitalvisionIf damaged:visual field loss,visual agnosia
Higher deficits shape rehabilitation. Neglect, aphasia and memory loss change how you instruct and motivate patients.
FunctionKey structuresClinical note
LanguageLeft frontal and temporal areas in most peopleUse short sentences and gestures in aphasia
MemoryHippocampus and medial temporal lobeWrite programmes down; repeat key points
AttentionFrontal and parietal networksReduce distractions; check neglect
Executive functionPrefrontal cortexBreak tasks into steps
SleepHypothalamus and brainstemPoor sleep worsens pain, mood and learning

Learning strengthens synapses through repeated activation, a process called long-term potentiation. Sleep helps consolidate new motor and verbal memories.

Exercise and the brain

Northey and colleagues pooled 36 trials in adults over 50 [1]. Exercise improved cognitive function regardless of participants’ cognitive status [1].

Figure 4 · Exercise improves cognition after 50

Pooled effect and prescription features of exercise for cognitive function Thirty-six studies with 333 effect sizes showed exercise improved cognition by a standardised mean difference of 0.29. Aerobic, resistance, multicomponent and tai chi training all helped; sessions of 45 to 60 minutes at least moderate intensity were associated with benefit. Studies / effect sizes36 / 333Overall effect on cognitionSMD 0.29 (0.17 to 0.41)Effective exercise typesaerobic, resistance, multicomponent, tai chiSession length45–60 minIntensityat least moderateBenefit was independent of cognitive domain and cognitive status [1]
Prescribe aerobic and resistance exercise of at least moderate intensity on as many days as feasible [1].

Erickson and colleagues randomised 120 older adults to aerobic training or control [2]. Training enlarged the anterior hippocampus by about 2% and improved spatial memory [2].

Figure 5 · Exercise grows the hippocampus

Hippocampal volume change with aerobic training versus control in older adults Aerobic exercise training increased anterior hippocampal volume by about 2 per cent, reversing age-related loss by one to two years and improving spatial memory, while volume declined in the control group. Gains were associated with higher BDNF. +2%Aerobic trainingolder adultsControl: declinedHippocampal volume changeReversed age-related lossby about 1–2 yearsSpatial memory improvedVolume gain tracked serumBDNF, a growth factor120 older adults, randomised [2]
The brain responds to training. Higher fitness also partly protected against volume loss in the control group [2].

Practical skill · teaching patients with cognitive or sensory deficits

Face the patient, speak clearly and check hearing aids and glasses. Demonstrate as well as explain. Use one-step instructions, written sheets and repetition.

Clinical relevance for the physiotherapist

  • Visual fields. Screen after stroke; teach scanning.
  • Hearing and vision. Check aids before exercise and falls assessment.
  • Neglect and aphasia. Adapt instructions and environment.
  • Brain health. Recommend aerobic and resistance exercise of moderate intensity [1].
  • Memory. Aerobic training can enlarge the hippocampus in older adults [2].

Assessment and application

SituationInterpretationAction
Stroke patient bumps into the left door frameLeft hemianopia or neglectField and neglect tests; scanning training
Older adult with memory complaintsPossible cognitive declineModerate aerobic and resistance exercise [1, 2]
Patient follows gestures but not speechReceptive aphasiaDemonstrate; simplify language
Patient keeps forgetting the home programmeMemory limitationWritten and picture handouts; fewer exercises

Common mistakes

  • Mistaking hearing loss for confusion.
  • Missing hemianopia in a patient who keeps falling.
  • Giving long verbal instructions to a patient with aphasia.
  • Ignoring cognitive benefits when prescribing exercise [1].
  • Assuming the ageing brain cannot change [2].

Exam preparation

Long answer

Describe the visual pathway and the effects of lesions at different levels.

  • Receptors: rods and cones (table).
  • Pathway and crossing at the chiasm (Figure 2).
  • Field defects at each level.
  • Clinical relevance after stroke.

Short notes

  • Types of hearing loss.
  • Aphasia.
  • Long-term potentiation.
  • Exercise and cognition [1].

Viva and practical

  • “Where do nasal fibres cross?” — at the optic chiasm.
  • “Which area controls speech output?” — Broca’s area.
  • “Can exercise improve memory?” — yes; hippocampus grew by 2% [2].
  • OSCE: test visual fields by confrontation.

Current evidence

Exam and traditional teaching

Cognitive decline with age is inevitable and unrelated to physical activity.

What the evidence adds

Exercise improves cognition in adults over 50 [1].

Aerobic training can reverse hippocampal shrinkage and improve memory [2].

What the student should understand

Movement is medicine for the brain as well as the body.

Check yourself

10 questions on this page. Tap one to see the answer and the reasoning.

Q1. Exercise improved cognitive function in adults over 50 by a standardised effect of about:
  1. (A) 0.03
  2. (B) 0.29
  3. (C) 2.9
  4. (D) No effect

Answer: (B) The pooled effect was 0.29 (0.17 to 0.41) [1].

Q2. Which session duration was associated with cognitive benefit?
  1. (A) 5–10 min
  2. (B) 45–60 min
  3. (C) 3 hours
  4. (D) Duration did not matter

Answer: (B) Sessions of 45–60 minutes were associated with benefit [1].

Q3. What intensity was associated with cognitive benefit?
  1. (A) Very light
  2. (B) At least moderate
  3. (C) Only maximal
  4. (D) Intensity was irrelevant

Answer: (B) At least moderate intensity [1].

Q4. Which exercise types had significant effects on cognition?
  1. (A) Only aerobic
  2. (B) Aerobic, resistance, multicomponent and tai chi
  3. (C) Only tai chi
  4. (D) None

Answer: (B) All four types had significant point estimates [1].

Q5. Did the cognitive benefit depend on participants' cognitive status?
  1. (A) Yes, only in dementia
  2. (B) No, it was independent of cognitive status
  3. (C) Only in healthy people
  4. (D) Not tested

Answer: (B) Effects were independent of cognitive domain and status [1].

Q6. Aerobic training increased hippocampal volume by about:
  1. (A) 0.2%
  2. (B) 2%
  3. (C) 20%
  4. (D) It decreased

Answer: (B) Hippocampal volume increased by 2% [2].

Q7. This increase reversed age-related volume loss by about:
  1. (A) 1–2 months
  2. (B) 1–2 years
  3. (C) 10 years
  4. (D) None

Answer: (B) It reversed age-related loss by 1–2 years [2].

Q8. The volume increase was associated with higher levels of:
  1. (A) Cortisol
  2. (B) BDNF
  3. (C) Insulin
  4. (D) Creatinine

Answer: (B) Greater serum BDNF [2].

Q9. Which memory function improved with the hippocampal change?
  1. (A) Spatial memory
  2. (B) Smell memory
  3. (C) Muscle memory only
  4. (D) None

Answer: (A) Spatial memory improved [2].

Q10. Which brain structures were unaffected by the exercise intervention?
  1. (A) Anterior hippocampus
  2. (B) Caudate nucleus and thalamus
  3. (C) All structures
  4. (D) Cerebellum and pons

Answer: (B) Caudate and thalamus volumes were unaffected [2].

Quick review

Key takeaways

  • Rods for dim light; cones for colour and acuity.
  • Chiasm lesion: bitemporal; tract or radiation: homonymous hemianopia.
  • Cortical lobes have distinct functions and deficits.
  • Exercise improves cognition, SMD 0.29 [1].
  • Aerobic training enlarged the hippocampus by 2% [2].
  • Adapt teaching to sensory and cognitive limits.

Further reading

SourceWhy it earns its place
Northey JM et al. — Br J Sports Med, 2018Exercise and cognition [1]
Erickson KI et al. — PNAS, 2011Exercise and the hippocampus [2]
Kandel, Principles of Neural ScienceSpecial senses and cognition

References

  1. Northey JM, Cherbuin N, Pumpa KL, Smee DJ, Rattray B. Exercise interventions for cognitive function in adults older than 50: a systematic review with meta-analysis. British Journal of Sports Medicine. 2018;52(3):154–160. doi:10.1136/bjsports-2016-096587 PMID 28438770 Systematic review and meta-analysis
  2. Erickson KI, Voss MW, Prakash RS, et al. Exercise training increases size of hippocampus and improves memory. Proceedings of the National Academy of Sciences USA. 2011;108(7):3017–3022. doi:10.1073/pnas.1015950108 PMID 21282661 Randomised controlled trial

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Reviewed by the Physiotherapist India Team. · Human Physiology contents