Brain and Behaviour 1 Flashcards
With regard to rats, define IC.
Isolated conditions
With regard to rats, define SC.
Social conditions
With regard to rats, define EC.
Enriched conditions
Define behave.
Act or function in a particular way
Define behaviour.
Response to a stimulus
Define behaviours.
What we see, we cannot see their motivation
Define motivate.
To give reason or inspiration for a course of action
Characterize an IC rat.
More aggressive, less motor activity, higher cortisol, higher body weight, smaller brains
Characterize an EC rat.
Friendly, more motor activity, cope with change better, thick cerebral cortex, increased synapse:neuron ratio
Describe an example of human IC/EC differences, and possible explanations.
US children in Vietnam, some returned to US, some remained. US children had higher DQ - could be cultural bias? Vietnam children has lower DQ - could be lower rate of maturation, possibly due to malnutrition?
What does cerebellum mean?
Little brain
What proportion of the brain is cerebellum?
11%
Proportionately, how many neurons are in the cerebellum compared to the brain?
More neurons than the rest of the brain put together
What inputs into the cerebellum (generally)?
Cerebral cortex, brain stem nuclei and sensory receptors
What does the cerebellum do?
Co-ordinates voluntary motor movement, balance, equilibrium and muscle tone
What does the cerebellum consist of?
Midline body and two lateral lobes separated by a deep cleft into which projects the falx cerebelli
Where is the cerebellum?
Occupies most of the posterior cranial fossa, resting on its floor, separated from the occipital lobe by transverse fissure and tentorium cerebelli
Describe the structure of the cerebellum.
3 layers - molecular, purkinje and granule (outer to inner)
Describe the inputs into the cerebellum.
Mossy fibred, via the middle peduncle, and climbing fibres, via the inferior peduncle
What is the main output of the cerebellum.
Purkinje cell axons from dentate to nucleus
What are the three peduncular connections from the cerebellum?
Superior link with nuclei in the midbrain, diecephalon and cerebrum; middle link with pons and midbrain; inferior link with nuclei in medulla as well as ascending and descending cerebellar tracts to/from the spinal cord
Where do climbing fibres to the cerebellum come from?
Olivocerebellar nuclei via the inferior cerebellar peduncle
What does the inferior cerebellar peduncle connect? What does this connection convey?
Medulla and cerebellum conveying muscle proprioception and vestibular inputs
Where do mossy fibres come from?
Pons and elsewhere via middle cerebellar peduncle
What does the middle peduncle connect? What information does this send?
Pons and cerebellum telling cerebellum of voluntary motor output
Where do most Purkinje cell axons go?
Dentate nucleus deep to cerebellar cortex (except from vermis)
Where do most Purkinje cell axons go after entering the cerebellum?
Superior cerebellar peduncle to decussate and pass to thalamus and red nucleus
What does the superior peduncle connect? Are connection mainly afferent or efferent?
Midbrain and cerebellum - efferent
What other cerebellar nuclei receive vermal Purkinje cell outputs?
Emboliform, globose, fastigial
What does cerebellar injury result in?
Movements that are slow and unco-ordinated
Damage to the cerebellum can lead to what?
Asynergia, dysmetria, adiadochokinesia, intention tremor, ataxic gait, hypotonia, ataxic dysarthria, nystagmus
Define asynergia.
Loss of co-ordination of motor movement
Define dysmetria.
Inability to judge distance and when to stop
Define adiadochokinesia.
Inability to perform rapid alternating movements
Define ataxic gait.
Staggering, wise based walking
Define hypotonia.
Weak muscles
Define ataxic dysarthria.
Slurred speech
Define nystagmus.
Abnormal eye movements
What are the effects of under nutrition on the adult body?
Significant reduction in body weight but less effect on the brain
What is the vulnerable period hypothesis?
Growing brains are much more vulnerable than adult brains to nutritional restriction
What does under nutrition during the period of rapid growth in the brain do?
Creates deficit, changing the relationships between features, and distortion
What does under nutrition do to cerebral growth? What effect does this have?
Reduces growth of axons and dendrites more than cell bodies, thus paradoxical increased in neuronal density
What are the two types of aggression?
Predatory - hunt for food; affective - posturing
What two things do all forms of aggression involve?
Motor system and ANS
Characterize a predatory aggression.
Relatively quiet; attacks to head and neck of prey; low levels of sympathetic activity
Characterize an affective aggression.
Noisy; unfocussed; high levels of sympathetic activity
What can simulate aggression?
Electrical stimulation of the amygdala
Where is the amygdala?
Sits in the medial part of the temporal lobe
What are the two main connections between the amygdala and hypothalamus?
Ventral amygdalofugal pathway and the stria terminalis
Describe the amygdala.
Almond shaped, consisting of 3 groups of nuclei - basolateral, corticomedial and central
What are the 3 groups of nuclei in the amygdala?
Basolateral, corticomedial and central
What can reduce aggression?
Bi-lateral lesions to the amygdala
What can reduce fear?
Bi-lateral lesions to the amygdala
What do bi-lateral lesions of the amygdala do?
Flattens emotion; reduces the ability to recognise facial expressions of emotion
What does the amygdala most respond to?
Faces showing fear more than any other emotion
When aspects of fear are learnt, what inputs into the amygdala?
Any stimulus is received by the inferior basolateral nuclei
When aspects of fear are learnt, what outputs from the amygdala?
Basolateral nuclei to the cerebral cortex carries emotion; central nucleus to PAG in the brainstem carries behaviour; central nucleus to hypothalamus carries any autonomic response
What other areas of the brain have been implicated in aggression?
Hypothalamus and PAG
What does PAG stand for?
Periaquaductal grey matter of the brainstem
What are the two connections from the hypothalamus to the mid-brain?
Medial forebrain bundle; lateral hypothalamus to ventral tegmentum
What kind of aggression is the hypothalamus associated with?
Predatory
What lesion to the hypothalamus can reduce aggression?
Dorsal longitudinal fasiculus from medial hypothalamus to PAG
What drug appears to have a role in the regulation of aggression?
Serotonin
What happens to aggression when serotonin synthesis is pharmaceutically blocked?
Increased levels of aggression
Why is the MRI safe?
Does not use ionising radiation like X-rays or CT scans
What does CT stand for?
Computed tomography
What particle does the MRI elicit a signal from?
Protons
Describe the MRI scanner.
Super cooled by liquid nitrogen, super-conducting coil; little resistance, little energy required
What does the scanner emit?
Powerful static magnetic field up to 9 tesla
In an MRI, which way do the protons naturally align?
Vertically
What is applied in an MRI to precess the protons?
Horizontal magnetic pulse applied at radio frequencies to make them wobble on their axes
What happens when a horizontal magnetic field is applied in an MRI?
All protons rotate horizontally in phase
What happens when a horizontal magentic field is disabled in an MRI?
Protons begin to de-phase from the horizontal position, leading to a loss of magnetisation
What is T2?
The time constant of the weaking field after a horizontal magnetic field has been disabled
What is the constant given to the time it takes for the weakening field in an MRI?
T2
What is T1?
The time it takes for the protons to re-align with the master field (vertically)
What is the constant given to the time it takes for protons to stand up in an MRI?
T1
What information is used to create the image in an MRI?
T1 and T2 graphs
What do T1 and T2 values depend on?
Surrounding matter - whether it causes de-phasing/realignment to happen quicker/slower; the different levels of brightness assigned
What is the theory behind fMRI?
Diameter of cerebellar arterioles slowly increases during cognitive applications, specific to task; deoxygenated blood is paramagnetic, oxygenated is not, thus deoxygentated blood can be detected
What possible reasons are there for increased blood flow to working areas of the brain?
Supply of nutrients/oxygen or to flush away metbolic by-products
What is the BOLD signal?
Blood oxygenation level dependent signal
What does the BOLD signal show?
Which part of the brain is active in almost anatomical detail
What kind of blood is detectable in an MRI, and why?
Deoxygenated, because it is paramagnetic
How is an fMRI image constructed?
Computer differentiates differences in magnetic field of blood, and displays image accordingly
What programs are used to create fMRI images?
Statistical parametric mapping (Windows) or FSL (Apple)
How does a computer map an fMRI image?
Calculates the probability that a voxel (small chunk) has a different BOLD signal than the next, using a t-test; each probability is assigned a colour, which is then overlaid on the anatomical MRI, mapping the activation
What controversial about the nature of the BOLD signal?
Some think it has nothing to do with the nutrition to the brain; increased blood flow far exceeds requirements, so maybe it is a cooling system
What is a voxel?
3D pixel of the brain
What does SPM stand for?
Statistical parametric mapping
What are the problems with fMRI?
Patterns of activation can vary in 10% of subjects performing the same task; applied to a standard template, the process can distort the image making it fuzzy
What two things does controlling a muscle require?
Excitation and feedback
What two anatomical features provide feedback from muscles?
Muscle spindle and Golgi tendon organ
What three locations do muscle spindles give muscle length information?
Spinal cord - basic processing; cerebellum - 2nd level processing; ‘higher centres’ - such as the motor cortex
What information does the muscle spindle feeback?
Length of muscle
What information does the Golgi tendon organ feedback?
Tension and rate of change of tension of the muscle
What shape are muscle spindles?
Fusiform
Only under what circumstances are muscle spindle useful?
When they are under tension
What are internal muscle spindle fibres called?
Intrafusal
What are external muscle spindle fibres called?
Extrafusal
What do extrafusal muscle spindle fibres do?
Relay the force of contraction to the brain
What two types of intrafusal muscle spindle fibres exist?
Bag and nuclear chain
Describe group Ia afferent muscle spindle axons.
Anulospiral, wrapped around the middle of both bag and nuclear chain intrafusal muscle fibres
How do gorup Ia afferent muscle spindle axons relay information?
Pulling apart the coils initiates action potentials
What is the appoximate conduction velocity of group Ia afferent muscle spindle axons?
240mph
Describe group II afferent muscle spindle axons.
Flower spray terminal end, embedding in middle regions of bag fibres; have some anulospiral endings confined to nuclear chain fibres
What kind of muscle spindle information do group Ia axons relay?
Dynamic phase of muscle stretch, i.e. as stretch is occuring
What kind of muscle spindle information do group II axons relay?
Static phase of muscle stretch, i.e. its final length
How does the muscle spindle maintain its tension?
When extrafusal fibres contract, gamma-motorneurones co-activate with alpha-motorneurones and spindle shortens in register with extrafusal fibres
What are the two sub-types of bag muscle spindle fibres?
Dynamic and static
What are the two sub-types of nuclear chain spindle fibres?
Long and short
What class of motorneurones control spindle length?
Gamma motor neurones
What is different about the muscle spindle contraction from the muscle contraction?
Muscle spindle contracts further to maintain its tension
What increases gamma neuron activity?
Serotonin (5-HT)
What decreases gamma neuron activity?
Noradrenaline
What happens when gamma neurons receive 5-HT?
Stimulation - intrafusal fibres become more stiff and more information is conveyed
What happens when gamma neurons receive noradrenaline?
Inhibtion - intrafusal fibres become more elastic and less information is conveyed
What is unique about the tendon jerk reflex?
The only monosynpatic reflex in the body
Describe the physiological steps in the tendon jerk reflex response.
Muscle stretched by hammer blow to its tendon; group Ia neurons fired to spine; synapses directly with alpha afferents of homonymous muscle; muscle contracts to counter stretch
Describe the Jendrassik’s manoeuvre.
Patient pulls arms against each other or clenches their jaw together
What does the Jendrassik’s manoeuvre cause?
Excitation in upper segments of the spinal cord - C5 - which spills over to the rest of the spinal cord
What happens to alpha-motorneurons following the Jendrassik’s manoeuvre?
Brought slightly toward threshold and is more excitable
What name is given by medics to the effect Jendrassik’s manoeuvre creates?
Facilitation
Why is Jendrassik’s manoeuvre useful in a clinical setting?
Useful for people with lesser reflexes
What famous scientist is often referred to as the Father of neuroscience?
Sherrington
What new and novel model did Sherrington use to study the stretch reflex?
Decerebrate cat
What was surgically done to a cat to make it decerebrate?
Surgical transection at level of midbrain, between the superior and inferior colliculi
What three connections does a spindle Ia neuron make?
Excitatory to homonymous muscle; excitatory to synergistic muscle; inhibitory to antagonistic muscle
What is a homonymous muscle?
The same muscle a neuron has left, i.e. Ia neurons often feedback to the same muscle they relay information
What is another name for the somatosensory system?
Dorsal column medial lemniscal system
How many synaptic relays are in the main somatosensory pathway?
Three
Where are the three main synapses in the somatosensory pathway?
Gracile and cuneate nuclei in the lower medulla; ventral posterior lateral nucleus of the thalamus; primary somatosensory cortex
Describe the main somatosensory pathway.
Entry into the spinal cord at the dorsal root ganglion, at the gracile and cuneate fascicle; ascension into lower medulla, with synaptic connection to the gracile and cuneate nuclei; decussation and ascension through medial lemniscus in upper medulla, pons and then midbrain; ascension into thalamus and synaptic connection with ventral posterior lateral nucleus; projection and synaptic connection to postcentral gyrus (somatic sensory cortex)
How many somatosensory corteces are ther?
Two - primary and secondary
Where are the somatosensory corteces?
Anterior parietal lobe and posterior parietal cortex
Which sulcus is the secondary somatosensory cortex in?
Deep in the lateral sulcus
What does lesioning of the primary somatosensory sulcus produce?
Proprioceptive deficits, inability to discriminate size, texture and shape of objects
How many regions is the primary somatosensory cortex divided into?
Four
What is the name given to the four somatosensory cortex divisions?
Cytoarchitectonic regions
What is the incidence of schizophrenia?
1%
What is the gender incidence of schizophrenia?
Men slighly more than women
What are ‘prodromal signs’?
Preceding signs of schizophrenia
List the positive signs of prodromal signs
Social isolation and withdrawal, impairment in normal fulfilment of expected roles, odd behaviours and ideas, neglect of personal hygeine, blunted affect
What follows prodromal signs in schizophrenic patients?
Positive signs - presence of distinctively abnormal behaviours
List the positive signs of schizophrenia
Loss of reality testing, memory disturbances, delusions, hallucinations, odd posture
Schizophrenic episodes can be seperated by what?
Period where the patient isn’t overtly psychotic, but displays negative signs
What are negative signs in schizophrenic patients?
Absence of normal social and interpersonal behaviours
List negative signs of schizophrenia
Exccentric, socially isolated, low levels of emotional arousal, impoverished social drive, poverty of speech, poor attention span, lack of motivation
What is the modern diagnostic criteria for schizophrenia?
Continuous illnes for 6 months with at least one psychotic episode that must include one or more of delusions/prominent/disorderered thoughts
What three categories can schizophrenia be split into?
Paranoid, disorganised and catatonic
Characterise paranoid schizophrenia.
Usually men, systematic delusions of persecution predominate
Characterise disorganised schizophrenia.
Early onset, wide range of symptoms, profound deterioration of personality
Characterise catatonic schizophrenia.
Rare form - mutism, abnormal posture predominates
What is the monozygotic incidence of schizophrenia?
45%
What is the dizygotic incidence of schizophrenia?
15%
What is the incidence of schizophrenia amongst parents, children and siblings of sufferers?
15%
What anatomical abnormalities characterise schizophrenia?
Reduced blood flow to globus pallidus, reduced increase in blood flow to working memory lobes, thinner medial temporal lobe, smaller anterior hippocampus, lateral and third ventricles enlarged
Outline the two step model of schizophrenia.
Genetic predisposition with envirnomental activation
What environmental factors are supposed to cause schizophrenic activation of genetic predisposition?
Developmental absnormality, viral infections, perinatal injury, lifestyle activities
What developmental abnormality is implicated in schizophrenia?
Number of cells just below cortical layer VI in superficial white matter of prefrontal and temporal lobes has migrated 3mm or so deeper
What is suggested as a trigger for schizophrenic developmental disturbances?
Exposure to influenze or premature switching off of genes involved in cell migration
What is the name of drugs used to treat schizophrenia?
Antipsychotics
What is the first choice of drug for schizophrenia?
Chlorpromazine
What type of drug is chlorpromazine?
Antipsychotics
What is chlorpromazine used to treat?
Schizophrenia
What are the specific anti-psychotic actions of chlorpromazine?
Abolishes delusions/hallucinations and some types of disordered thinking
What is the MOA of chlorpromazine?
Blockage of dopamine receptors
What is the MOA of phenothiazines?
Blockage of D1/2
What is the MOA of thioxanthenes?
Blockage of D1/2
What is the MOA of butyrophenones?
Blockage of D1/2
What is the MOA of clozapine?
Blockage of D2/3/4
Where are D1 and D5 receptors mainly expressed?
Cortex and hippocampus
Where are D2/3/4 receptors mainly expressed?
Caudate nucleus, putamen, nucleus and accumbens
Where are D3/4 recetors mainly expressed?
Limbic system, cortex and weakly in basal ganglia
What families of drugs are ‘typical’ antipsychotics?
Butyrophenones and thioxanthenes
What type of antipsychotics are butyrophenones and thioxanthenes?
Typical antipsychotics
Name three ‘atypical’ antipsychotics
Clozapine, risperidone, olanzipine
What are the advantages of using ‘atypical’ antipsychotics?
Fewer side effects
What are extrapyramidal effects also known as?
Side effects
What are the three levels of motor control?
Highest level - primary motor cortex, middle level - brainstem, lowest level - spinal cord
How does the primary motor cortex link into motor control?
Projects straight to spinal cord via corticospinal tract, regulates the motor tracts that originate in brainstem
How does the brainstem link into motor control?
Lateral descending system controls distal limbs is important for goal orientated movements
How does the spinal cord link into motor control?
Mediate reflexes, mostly polsynaptic synapses, some mono-synaptic
How was Brodmann’s area 4 discovered?
Area of the brain where lowest intensity of stimulation elicited movement
What is another name for the motor cortex?
Brodmann’s area 4
Where is the primary motor cortex?
Located just before central sulcus, sometimes called the precentral gyrus to highlight its position
What limbs have disproportionate representation in the primary motor cortex?
Fingers/hands/face have disproportionately large representation
What is another name for the first motor cortex neurones?
Upper motor neurones
What does UMN stand for?
Upper motor neurones
What are UMN involved in?
Planning, initiating and directing movements
What do UMN synapse with?
Lower motor neurones
What does LMN stand for?
Lower motor neurones
What are lower motor neurones otherwise known as?
Final common pathway
What does the final common pathway innervate?
Muscles
The primary motor cortex is hierarchical, but what happens if you artificially stimulate it?
Brain stem and spinal cord just twitch
Why is direct stimulation not enough for hierarchical control of the motor system?
Other structures required to co-ordinate movement
What other structures are required to co-ordinate movement?
Basal ganglia and cerebellum
How do the ganglia and cerebellum help co-ordinate movement?
Receive information from many other cortical inputs through thalamus and they monitor the situation the person is in; if inappropriate signals are sent, they correct and submit to the PMC for approval before muscle override
What does PMC stand for?
Primary motor cortex
What does the basal ganglia comprise?
Caudate, putamen, substantia nigra, subthalamic nuclei
