HC1 Introduction Flashcards
Cognitive neuropsychology
The study of the relation between structure and function of the brain and specific cognitive functions (e.g. language, memory, attention, …)
Cognitive neuropsychology research
- By investigating these cognitive processes in normal healthy people.
- By investigating the breakdown of these processes in brain-damaged individuals (as a result of acquired brain damage or as a result of a developmental disorder).
Brain enthusiasm
- Brain scans as evidence in court of law
- Brain scans might be overinterpreted by laypersons.
- Good progress for several neurological syndromes, but less progress for psychiatric and mental syndromes.
Neurons
Contain with cell bodies in grey matter of cerebral cortex and subcortical structures
Axons
Contained by white matter
Neuron without input
Without input (at rest), cell membrane of a neuron has
an electrical potential difference between in- and outside of -70 mV
Post-synaptic potential
Is determined by integrating input of many synapses at the dendrites. It can hyper and depolarize.
Neural communication
o Input neurons (through neurotransmitters): action potentials over time
→ Membrane potential of post-synaptic neuron depolarizes or hyperpolarizes
o Over time, membrane potential of post-synaptic neuron changes in function of input it receives = signal
Simplest signal
Sinusoidal oscillation
Frequency
Rate of change of signal, e.g. in the time dimension
o 1 Hz = completing a full cycle (going up & down) in one second
o Biological signals never contain just one frequency
Complex signals can be decomposed into..
Frequency components
Each has a particular frequency (e.g., 1 Hz, 2 Hz, 3 Hz, …)
Amplitude
How much it goes up and down
Phase
When it goes up and down
Frequency spectrum
Measured range of frequencies
Highest frequency
▪ Limited by sampling frequency
▪ ½ * sampling frequency (Nyquist sampling theorem)
Lowest frequency
▪ Limited by how long the signal is measured
▪ 1 / number of seconds measured
Filtering
Attenuating or excluding certain part of measured frequency spectrum (low-pass, high-pass or band-pass)
Spectrogram
Strength of each signal component at each moment in time
Electrophysiological changes are connected to other kind of changes: at a SMALLER scale
Movement of chemical substances and molecules
▪ E.g. depolarization: influx of Na+, repolarization: outward current of K+
▪ E.g. calcium concentration high in electrically active neurons → two-photon calcium imaging
Electrophysiological changes are connected to other kind of changes: at a LARGER scale
Hemodynamics
▪ Blood supply is adjusted to current energy needs
Energy consumption
o Electrophysiological events require energy
o Amplitude of potential changes not necessarily best predictor of energy consumption
▪ Action potential
o Restoring resting potential requires energy → energy consumption of neuron could correlate with number of action potentials
o Pre- and post-synaptic factors (e.g., neurotransmitter release) also require energy
o Exact energy distribution to different processes can vary (species, neuron type)
Action potential
Passive chain of events that does not consume much energy
Maps in the brain - Clustering
Noninvasive methods cannot achieve single neuron resolution
▪ Methods with highest spatial resolution still average signal from many neurons.
Maps in the brain - Neurons of similar functional properties are clusrered together
o The more clustering, the more the averaged signal from many neurons corresponds to the signal of the individual neurons → sensitivity of a noninvasive imaging technique depends upon amount of clustering present
o Clustering on different spatial scales
▪ Topographic areas: for example the somatosensory homunculus but also for auditory or occipital information
