L1: Cognitive Neuroscience Flashcards
Dehaene et al 2004
- fMRI study carried out
- found that specific area of the brain activated
- if the brain exposed to the word for the first time its activation levels are greater then when exposed to same word again
- brain vs cognitive psychology findings
Methods for looking at the brain
- Single unit recording
- Electroencephalography (EEG)
- Magnetoencephalography (MEG)
- Positron Emission Tomography (PET)
- Magnetic Resonance Imaging (MRI)
- Functional MRI – fMRI
- Diffusion Tensor Imaging – DTI
do we need to learn….
• Functional Near-Infrared Spectroscopy – fNIRS
• Intracranial electroencephalography (iEEG) - ECoG
Electroencephalography (EEG):
measurements of electrical signals generated by the brain through electrodes placed on different points on the scalp.
(non-invasive)
- high temporal acuity
Event-related potential (ERP)
the average amount of change in voltage at the scalp that is linked to the timing of particular cognitive events
single-cell recordings
measure the responsiveness of a neuron to a given stimulus (in terms of action potentials per second)
(invasive method)
how are single-cell recordings made:
intracellular recording: implanting a v small electrode into the neuron
extracellular recording: implanting a small electrode outside the membrane
Magnetoenecephalography (MEG)
an imaging technique that measures magentic fields produced by electrical activity in the brain - using devices known as SQUIDs.
- good temporal AND spatial resolution and NON INVASIVE
- v expensive and lacks accessibility.
rate coding:
the informational content of a neuron may be related to the number of APs per second
temporal coding:
the synchrony of firing may be used by a population of neurons to code the same stimulus or event
dipole
a pair of positive and negative electrical charges separated by a small distance.
slowest to fasted EEG frequencies:
the EEG signal tends to oscillate at different rates
slowest to fastest:
- delta
- theta
- alpha
- beta
slowest to fasted EEG frequencies:
the EEG signal tends to oscillate at different rates
slowest to fastest:
- delta
- theta
- alpha
- beta
what do ERPs tell us:
variations in the ERPR waveform tell us about the TIMING and INDEPENDENCE of cognitive processes.
structural versus functional imaging
structural: different types of tissue (skull, gray matter, CSF fluid) have different physical properties used to create STATIC maps (CT and structural MRI)
Functional: based on the assumption that temporary neural activity produces local physiological changes in that region of the brain. (PET and fMRI)
Positon Emission Therapy (PET)
- measures local blood flow (rCBF)
- radioactive tracer injected into blood stream
- areas with high radioactivity - associated with high brain activity - based on blood volume
- more red in image = more blood flow.
fMRI
- directly measures conc of deoxyhaemoglobin in the blood
- this is called blood oxygen level dependent contact (BOLD response)
- the change in BOLD response over time is called the haemodynamic response function
- the haemodynamic response function peaks in 6-8s - limiting the temporal resolution of fMRI.
difference between fMRI and PET
- PET measures the change in blood flow to a region directly
- fMRI measures the richness of the blood in oxygen
both are haemodynamic methods though
voxel-based morphometry (VBM)
- a technique for segregating and measuring differences in white matter and gray matter concentration
diffusion tensor imaging (DTI)
- uses MRI to measure white matter connectivity between brain regions
voxel
a volume-based unit in imaging research the brain is divided into many thousands of these.
cognitive subtraction
- an activity in a control task is subtracted from the activity in an experimental task
functional near-infrared spectroscopy (fNIRS)
- measures same BOLD response
- but in a different way - light in the infrared range passes through skull and scalp but is scattered differently by oxy- v. desoxyhaemoglobin
- cant image deep pictures but is portable and more tolerant to head movements
intracranical EEG or ECoG
