Brain & Language Exam 1

Cognitive neuroscience:

Studies the neural mechanisms underlying cognitive processes

• perception, attention, memory, and language

Neuropsych:

Cognitive and emotional defects in people with brain damage

What does modern cognitive neuro use?

Lesion studies, brain imaging, computational models

Phrenology

The idea that individual differences in cognition can be mapped on to differences in skull shape

Paul Broca

Evidence that a specific region of the brain is associated with language

Ventricles

Lateral: wing

Third: middle

Fourth: bottom

Contralateral

The opposite side

Ipsilateral

The same side

Unilateral

One side of the brain

Bilateral

Both sides of the brain

Proximal

Near

Distal

Far

Subcortical area

Deep in the brain

Where is the medulla?

Superior to spinal cord

Medulla’s function

• Where several cranial nerves originate

• Controls respiration and heart rate

Where is the pons?

Connects brain to cerebellum and cranial nerves

Pons’ function

Controls some eye movement and balance. Relays auditory info

Where is the cerebellum?

Behind medulla and pons

Cerebellum’s function

Regulates muscle tone, execute movements, maybeee language function

What contains ~80% of neurons?

Cerebellum

What is the thalamus shaped like?

Egg shaped, on top of brain stem

Thalamus’ function

Sensory gateway (minus smell)

Where is the hypothalamus?

Below the thalamus

Hypothalamus’ function

Maintains body’s internal environment, critical for homeostasis

Where is the hippocampus located?

Sausage-shaped structure

Hippocampus’ function

Spacial navigation and episodic memory, tracks distance between word meanings in semantic memory

Where is the amygdala located?

Almond-shaped structure

Amygdala’s function

Processes emotionally and socially relevant info, neg/life threatening facial expressions

What makes up the basal ganglia?

Caudate nucleus, putamen, globus pallidus

Basal ganglia function

Motor control, rewarding behaviors

Gyrus

Bump of brain

Sulcus

Vallies between bumps

Sulcus

Very deep fissure

Longitudinal fissure

Seperates left and right hemisphere

Central sulcus

Seperates front/parietal lobes

Lateral/syllivan fissure

Seperates each hemisphere in dorsal/ventral dimension (frontal, temporal)

What’s in the frontal lobe?

Primary motor region, premotor region, prefrontal region

Function of frontal lobe

Planning, guidance, decisoion making, language

Parietal lobe

Intergrates info, sensory world w/ memory, spatial reasoning

What does damage to the parietal lobe cause?

Apraxia, agraphia

Temporal lobe function

Memory, visual item recognition, auditory processing, emotion

Occipital lobe

Primary visual cortex (V1): basic shapes

Cortexes in occipital lobe

V2 and V4: orientation and color

V5: motion

V3: ?

Cytoarchitectonic organization

Similarities and differences between both cortical areas

Intracranial recording

Single cell recording

Local field potentials

Electrode grids placed over cortex - electrocorticography

Advantages of intracranial recordings

Only method in humans w/ high spatial and temporal resolution

Disadvantages of intracranial recordings

• Invaseive

• only possible in patients w/ neurological conditions

• data is rare and hard to get

Extracranial readings

Electroencephalogram (EEG)

EEG

Continuous trace of waveforms recorded from scalp electrodes, vary in aplmlitude and frequency

Neuron to EEG

1. postsynaptic potential

2. Dipoles

3. summation

4. scalp distribution

5. EEG waveforms

What gives rise to EEGs?

• post synaptic potentials

• aligned dipoles w/ synchronous behaviors, strong enough to reach scalp

ERPs

Fluctuating waveforms recorded from scalp electrodes; time locked w/ time of stimuli

Problem w/ ERPs

• metabloic regulation

• muscle movements

• talking from next room

• forgot to feed cat

• think about exam

ERPs are…

Averaged over events of same condition to reduce noise; reveals pattersn associated w/ event

ERP components

1. Polarity

2. Time course

3. Scalp distribution

4. Task/manipulation

Intracranial:

Single cell → action potential

• local field potential

Extracranial:

Post-synaptic potential

Why use ERPs?

• To index cognitive processes between the stimulus and when the response is made

• Different parts of waveform relate to cognitive processing stages

Forward problem

Source → scalp

• ERPs have very poor spatial resolution

Inverse problem

Scalp → source

• Advantages: good temporal resolution

• Disadvantages: different to determine neural generators of signals at scalp (poor spatial resolution)

Transcranial magentic stimulation

Mag field penetrates skull and alters cortical nerves

Magentic stimulation can be…

Disruptive (high intensity)

Facilitative (low intensity) → transcranial direct stimulation

Advantages of TMS:

• Good temporal resolution

• Good spatial resolution

• Reversible

Disadvantages of TMS:

• Limited depth

• Short lived

• Noise & discomfort

EPN:

Sensitive to emotion

LPC:

Sensitive emotion/attention

PET

Positron emission tomography

fMRI

Functional magentic resonance imaging

Shared principals of PET and fMRI

Regional changes in blood flow associated w/ neural activity

• Both indirect measures of brain activity

• Hemodynamic methods

How do PETs work?

Tracks radioactive isotope through brain (15O)

1. inject participants w/ tracer

2. blood region w/ high blood flow will accumulate more tracer

3. isotope decays → emits a positron → hits electrons → gamma photons

4. PET detects gamma photons, produces tracer conc. map

Spatial resolution of PET

10 mm

Temporal resolution of PET

30 s

Cons of PET

• Radiactive substance injections

• Decays in 10 mins

fMRI

Tracks “blood oxygenated level dependent” (BOLD) signal

Oxygemoglobin (HbO)

Not magentic

Deoxyhemoglobin (Hbr)

Paramagnetic

• Distorts magnetic field

How do you produce a stronger, clearer MR signal?

Areas w/ less deoxyhemoglobin produce a stronger, clearer MR signal

• This fluctuation is called the BOLD signal

Advantages of fMRI:

• Good spatial resolution → 3 mm or less

• Whole brain coverage: cortical and subcortical areas

• Non-invasive

Disadvantages of fMRI:

• Poor temporal resolution (2-6s behind neural activity)

• Indirect measure - inferred from hemodynamic changes

Coordinates of brain

Voxels: 3D x, y, z coordinate system

• Used to pinpoint region

• x axis: left-right

• y axis: anterior-posterior

• z axis: superior-inferior

Cognitive substraction:

Isolating neural correlates/function of specific cognitive capacities

Two key conditions of cognitive subtraction

• Experimental: requires ability of interest

• Control: doesn’t requirer that ability but is equivalent in all other aspects

Activation map of control

Experimental → brain areas unique to the ability of interest