The Body Senses and Movement

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CHAPTER 11

• The Body Senses and Movement
• Relation between Movement
• and Learning Disorders

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Parkinsons disease

• Parkinsons disease characterized by
• motor tremors
• Rigidity
• loss of balance and coordination,
• difficulty in moving, especially in initiating
  movements
• http//www.youtube.com/watch?vy1dkh2crci4
• The symptoms are caused by deterioration of the
  substantia nigra.
• neurons of the substatia nigra send
  dopamine-releasing axons to the striatum.
• The striatum is composed of the basal ganglias
  caudate nucleus and putamen and the nucleus
  accumbens.
• Upsets balance between direct and indirect
  pathways

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etiology

• Some forms likely genetic
• recent whole-genome study of Parkinsons patients
  identified 12 genes that likely contribute to the
  disease.
• Two of the implicated genes may play role in the
  development and programmed death of
  dopamine-producing neurons.
• Two others result in deviant proteins that are
  components of Lewy bodies
• Lewy bodies abnormal clumps of protein that form
  within neurons.
• Lewy bodies found in several brain locations in
  some Parkinsons patients
• Also found in people with form of dementia,
  dementia with Lewy bodies.
• Lewy bodies likely contribute to cognitive
  deficits and depression that often accompany
  Parkinsons disease.

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etiology

• Some forms likely genetic
• recent whole-genome study of Parkinsons patients
  identified 12 genes that likely contribute to the
  disease.
• Two of the implicated genes may play role in the
  development and programmed death of
  dopamine-producing neurons.
• Two others result in deviant proteins that are
  components of Lewy bodies
• Lewy bodies abnormal clumps of protein that form
  within neurons.
• Lewy bodies found in several brain locations in
  some Parkinsons patients
• Also found in people with form of dementia,
  dementia with Lewy bodies.
• Lewy bodies likely contribute to cognitive
  deficits and depression that often accompany
  Parkinsons disease.

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treatment

• Typically treated by administering levodopa
  (L-dopa),
• precursor for dopamine.
• Why use precursor?
• Dopamine not cross the blood-brain barrier
• L-dopa will
• in the brain is converted to dopamine.
• Problem
• treatments increase dopamine throughout brain
• causes side effects including restlessness,
  involuntary movements and hallucinations.
• As more neurons die, more drug is required,
  increasing the side effects.
• Eventually, no neurons left

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Huntingtons chorea

• Huntingtons disease
• degenerative disorder of the motor system
• cell loss in the striatum and cortex.
• Is genetic dominant gene trait
• Progressive disorder
• Onset typically in late 20s, early 30s
• Years before a diagnosis, begins with jerky
  movements that result from impaired error
  correction.
• At mid stage
• involuntary movements appear
• first as fidgeting
• then as movements of the limbs
• Late stage
• writhing of the body
• facial grimacing
• Loss of motor control and death

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Huntingtons

• Much more severe symptoms
• cognitive and emotional deficits are a universal
  characteristic of Huntingtons disease
• In contrast to other movement disorders such as
  Parkinsons.
• http//www.youtube.com/watch?vHP9YrOrpt3A
• Deficits include
• impaired judgment
• difficulty with a variety of cognitive tasks
• depression
• personality changes
• Motor symptoms are due to the degeneration of
  neurons in the striatum
• Defective or degenerated neurons in the cortex
  probably account for the psychological symptoms.

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etiology

• Huntingtons disease results for a mutated form
  of the Huntingtons gene.
• Is dominant trait gene
• If you have the gene, you will get the disease
• 50/50 chance of passing it on
• Ethical dilemma created with identification of
  gene
• The loss of neurons is probably due to the
  accumulation of the genes protein,
• Protein called huntington
• function is unknown.

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Myasthenia gravis

• Myasthenia gravis
• disorder or muscular weakness
• caused by reduced numbers of sensitivity of
  acetylcholine receptors.
• http//www.youtube.com/watch?v4lRBB-CFAn0feature
  related
• Drugs that inhibit the action of AChe give
  temporary relief from the symptoms of myasthenia
  gravis.
• Remember AChe breaks down Ach in synapse.
• Inhibitors increase amount of neurotransmitter
  available at the neuromuscular junction.

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Multiple sclerosis

• motor disorder with many varied symptoms
• caused by deterioration of myelin (demyelination)
  and neuron loss in the central nervous system.
• Demyelination causes slowing or elimination of
  neural impulses
• This reduces the speed and strength of movements.
• As the disease progresses, unmyelinated neurons
  die, leaving areas of sclerosis, or hardened scar
  tissue.
• muscular weakness, tremor, impaired coordination,
  urinary incontinence, and visual problems.
• Symptoms may wax and wane autoimmune reactions
• Several drugs are available modify immune
  activity in multiple sclerosis patients
• Slow the progress of the disease
• Do not repair the harm already done.

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Figure 11.23 The brain of a deceased MS
patient The arrows indicate areas of sclerosis,
or hardened scar tissue.
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Learning and motor disruptions

• Strong link between descending motor pathway
  abnormalities and a variety of genetic,
  behavioral, learning and psychological disorders.
  
• Learning and psychological disorders linked to
  descending motor pathway disturbances include
• dyslexia,
• Tourettes syndrome,
• several genetic forms of mental retardation,
• autism
• ADHD.
• The common link between all of these disorders
  Inability to appropriately inhibit some
  behavioral patterns while disinhibiting others.

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distonia

• Primary dystonia
• movement disorder resulting from basal ganglia
  dysfunction,
• may be related to ability to detect different
  emotional facial expressions.
• Patients with primary dystonia show
• isolated deficits in the recognition of disgust
• not happiness surprise, sadness or anger.
• Dystonia resulting from basal ganglia
  dysfunction
• not only motor dysfunction
• Also demonstrates role of the basal ganglia in
  cognitive behavior such as emotion recognition.

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22q11.2 deletion syndrome

• 22q11.2 deletion syndrome (22qDS).
• children show a wide spectrum of disabilities
• cognitive and motor deficits
• physical anomalies
• ADHD,
• poor executive visual attention,
• poor sensorimotor processing,
• learning disabilities with primary impairment in
  working memory.
• up to 25 times more likely to develop autism,
  pervasive developmental disorders, and
  schizophrenia.
• may have early functional abnormalities in
  corticostriatal pathways linking the prefrontal
  cortex and basal ganglia structures.

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Lesch-nyan syndrome

• Rare genetic disorder
• linked to descending motor pathway dysfunction
• caused by a mutation in the gene coding for the
  enzyme hypoxanthine-quanin phosphoribosyltransfera
  se
• characterized by
• hyperuricemia,
• motor disorders,
• severe and compulsive self mutilation.

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Lesch-nyan syndrome

• Why? disconnect between the prefrontal cortex
  and the basal ganglia
• caused by DA dysfunction
• results in a dysfunctional DA signal
  accidentally reinforces early injurious behavior
• Initial injurious behavior occurs because motor
  dysfunction resulting in clumsiness and awkward
  movements incidentally produce self injury.
• Behavior becomes well learned and automated
• Result Pattern of severe self mutilation.

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Lesch-nyan syndrome
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Tourettes syndrome

• Tourette syndrome (TS) characterized by
• stereotyped involuntary movements, or tics.
• Result of structural and functional abnormalities
  of the basal ganglia
• Link between motor system and limbic system is
  disturbed
• Result is spontaneous disinhibiton of competing
  motor and limbic system
• http//www.youtube.com/watch?vqjWdnQZGScs
• Treatment
• Typically antipsychotic medication (Dopamine D2
  antagonists) because reduce available DA in
  system
• Unfortunately, compound learning deficits
• Alternative biofeedback and learned control of
  tics

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Language disorders

• Language disorders may be due to poor regulation
  by the basal ganglia and related structures.
• May be Language disorder due to abnormal
  development of the basal ganglia
• Basal ganglia modulates Procedural memory
• modulates learning and execution of motor and
  cognitive skills
• Also critical for aspects of grammar.
• Lexical and declarative memory not affected
• these behaviors depend on other brain structures
• not affected by abnormalities in the
  frontal-subcortical network.

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Speech apraxia

• Speech apraxia
• Difficulty with pronunciation, production of
  speech
• particular phonemic characteristics of speech
  apraxia may be due to subcortical dysfunction.
• observations of those with speech apraxia reveal
• greater phoneme substitution errors
• errors occurred significantly more often in the
  initial rather than the medial or final word
  position.
• The speech errors likely due to disinhibition of
  competing phonemes during speech
• Suggests speech motor planning occurs at
  subcortical and cortical brain levels.

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stuttering

• link between stuttering and basal ganglia
  dysfunction.
• stuttering similar to other basal ganglia
  disorders such as Parkinsons disease and
  dystonia.
• stuttering is alleviated with interventions such
  as rhythm effects, chorus speech, and singing
  retraining brain

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stuttering

• Basal ganglia-thalamocortical motor circuits
  through the putamen likely play a key role in
  stuttering.
• Stuttering due to impaired ability of basal
  ganglia to produce timing cues for the initiation
  of the next motor segment in speech.
• Dysfunction due to abnormalities in the dopamine
  error-detection feedback system,
• Pharmacologic interventions such as DA
  antagonists thus effective in alleviating
  stuttering
• Also behavioral training programs

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adhd

• Descending motor system plays strong role in
  attention deficit disorder/hyperactivity disorder
  (ADHD).
• Neuropsychological studies show a pattern of
  cognitive deficits consistent with prefrontal
  executive problems
• Individuals with ADHD exhibit
• inattention,
• difficulty with self regulation,
• response inhibition deficits (impulsivity),
• restlessness or hyperactivity, and even apathy
• Individuals may show all or some of these
  behavioral deficits.

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adhd

• Exist at least two subtypes, according to the
  DSM-IV
• the inattention dimension
• hyperactive or impulsive dimension
• symptoms appear to be related to a latent trait
  of disinhibition,
• inattentive symptoms impact cognitive behaviors
  more than the impulsive subtype.

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ADHD

• ADHD disorder of self-regulation stemming from
  dysfunction of frontal-subcortical system.
• Total cerebral volume smaller in ADHD children
  than controls.
• Small, but significant reductions in mean total
  cerebral volume also found.
• Frontal lobe volume small is smaller in ADHD
  children
• Regions of the basal ganglia, particularly
  caudate nucleus, shown to be smaller in ADHD
  children

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ADHD

• Studies with typical children show that caudate
  size decreases as child matures- result of normal
  pruning of neurons.
• Children with ADHD appear to start out with
  smaller caudate nuclei,
• With maturation decline significantly greater
• The size differential of caudate nuclei between
  ADHD and typical children may increase with age.
• Right hemisphere structures more affected than
  left hemisphere structures for children with
  ADHD.
• Typically, right frontal area gtleft frontal area
• Right hemisphere important in regulating
  attention.
• May explain lack of attention regulation found in
  ADHD children

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ADHD

• Several other related structures appear to be
  abnormal in children with ADHD.
• relative decrease in size of cerebellum
• reduction in area of anterior or posterior corpus
  callosum
• ADHD may be due to a dysfunction of the
  prefrontal-subcortical system
• evidence points to greater dysfunction in right
  hemisphere.
• children with ADHD may have delayed development
  in their frontostriatal circuits.
• Why do DA agonists (ritalin, adderall) work
  speed up system!