TASK 4 Flashcards
HORMONES
A chemical secreted by cells that is conveyed by the bloodstream and regulates target organs or tissue.
Many hormones are produced by endocrine glands, sometimes also exocrine glands produce them.
Neurotransmitters belong to the nervous system and hormones to the endocrine system. Some neurotransmitters can also be hormones. Endocrine system is a collection of glands that produces hormones directly into the circulatory system to be carried towards other organs.
X-ray-based techniques
NON INVASIVE METHODS AND MEASURES
METHODS OF VISUALISING THE BRAIN
_Conventional x-ray
_Contrast x-rays
_Computed tomography (CT)
_Contrast x-rays
NON INVASIVE METHODS AND MEASURES
METHODS OF VISUALISING THE BRAIN
X-ray-based techniques
_injecting into one compartment of the body a substance that absorbs x-rays either less or more than the surrounding tissue
_cerebral angiography
_localizing vascular damage
_localization of a tumour through displacement of blood vessels
_Computed tomography (CT)
NON INVASIVE METHODS AND MEASURES
METHODS OF VISUALISING THE BRAIN
X-ray-based techniques
_computer assisted x-ray procedure that can be used to visualize the brain and other internal structures of the living body
_putting patient’s head in a rotating cylinder that takes 8-9 scans of horizontal brain sections that if combined can provide three-dimensional representations of the brain
Radioactivity-based technique
NON INVASIVE METHODS AND MEASURES
METHODS OF VISUALISING THE BRAIN
_Positron emission tomography (PET)
_Positron emission tomography (PET)
NON INVASIVE METHODS AND MEASURES
METHODS OF VISUALISING THE BRAIN
Radioactivity-based technique
_provides images of brain activity
_document the distribution of radioactivity in the brain
_radioactive fluorodeoxyglucose (FDG) is injected into the patient’s carotid artery (artery of the neck that feeds the ipsilateral cerebral hemisphere). Because of its similarity to glucose, the primary metabolic fuel of the brain, fluorodeoxyglucose is rapidly taken up by active (energy-consuming cells)
_each PET scan is an image of the levels of radioactivity (indicated by colour coding)
_each PET scan is merely a coloured map of the amount of radioactivity in each of the tiny cubic voxels (volume pixels) that compose the scan
_PET is recently used combined to MRI
_identify the distribution in the brain of molecules of interest (particular transmitters, receptors or transporters) , they inject volunteers with radioactively labelled ligands
Magnetic-field-based techniques
NON INVASIVE METHODS AND MEASURES METHODS OF VISUALISING THE BRAIN _magnetic resonance imaging _functional MRI (fMRI) _diffusor tensor imaging (DTI)
_magnetic resonance imaging (MRI)
NON INVASIVE METHODS AND MEASURES
METHODS OF VISUALISING THE BRAIN
Magnetic-field-based techniques
_structural brain imaging procedure in which high-resolution images are constructed from the measurement of radio-frequency waves that hydrogen atoms emit as they align with a powerful magnetic field
_provides a relatively high spatial resolution (the ability to detect and represent differences in spatial location)
_MRI can produce images in three dimensions
_functional MRI (fMRI)
NON INVASIVE METHODS AND MEASURES
METHODS OF VISUALISING THE BRAIN
Magnetic-field-based techniques
_it has even been used to communicate with patients in a vegetative state
_produces images representing the increase in oxygen flow in the blood to active areas of the brain
_active areas of the brain take up more oxygenated blood than they need for their energy requirements, and thus oxygenated blood accumulates in active areas of the brain
_the signal recorded by fMRI is called the BOLD signal (the blood-oxygen-level-dependent signal)
_fMRI has poor temporal resolution, that is, it is poor at specifying the timing of neural events. It takes 2 or 3 seconds to measure the BOLD signal and many neural responses, such as action potentials, occur in the millisecond range
FUNCTINAL MRI IS BETTER THAN PET
1- Nothing has to be injected into the volunteer
2- It provides both structural and functional information in the same image
3- Spatial resolution is better
4- It can be used to produce three dimensional images of activity over the entire brain
_diffusor tensor imaging (DTI)
NON INVASIVE METHODS AND MEASURES METHODS OF VISUALISING THE BRAIN Magnetic-field-based techniques _it is a variation of MRI _it is a method of identifying those pathways along which water molecules rapidly diffuse. Because tracts (bundles of axons) are the major routes of rapid water diffusion in the brain, diffusion tensor imaging provides an image of major tracts
Non-invasive stimulation
Play a major role in establishing the causal effects of human cortical activity on cognition and behaviour
_transcranial magnetic stimulation (TMS)
_transcranial direct current stimulation (tDCS)
_transcranial magnetic stimulation (TMS)
Non-invasive stimulation
_technique that can be used to turn OFF an area of human cortex by creating a magnetic field under a coil positioned next to the skull
_the magnetic stimulation temporarily turns off part of the brain while the effects of the disruption on cognition and behaviour are assessed
¬_TMS can also be used to turn ON an area of the cortex
_increases magnetic field, overstimulates the cells (artificial action potential) , the refectory period lasts longer more action potentials there are and afterwards the cells have to rest (no more action potential)
_transcranial direct current stimulation (tDCS)
Non-invasive stimulation
_technique that can be used to stimulate (turn ON) an area of the cortex by applying an electrical current through two electrodes placed directly to the scalp.
_electrical stimulation temporarily increases activity in part of the brain while the effects of the stimulation on cognition and behaviour are assessed.
PSYCHOPHYSIOLOGICAL MEASURES - brain activity
_scalp electroencephalography (EEG) _magnetoencephalography (MEG)
_scalp electroencephalography (EEG)
PSYCHOPHYSIOLOGICAL MEASURES - brain activity
_it is recorded through large electrodes by an electroencephalograph (EEG machine)
_each channel of EEG activity is usually recorded from disk-shaped electrodes, about half the size of a dime, which are attached to the scalp
_The scalp EEG signal reflects the sum of electrical events throughout the head. These events include action potentials and postsynaptic potentials as well as electrical signals from the skin.
_the utility of EEG is its value as a research and diagnostic tool rests on the fact that some EEG wave forms are associated with particular states of consciousness or particular types of cerebral pathology.
_alpha waves are regular, 8 to 12 per second. High amplitude waves associated with relaxed wakefulness
_record EEG activity simultaneously to indicate the origin of particular waves
_event related potentials (ERPs) , accompanying EEG background waves , they are related to certain psychological events. One commonly studied type of event related potential is the sensory evoked potential – the change in the cortical EEG signal elicited by the momentary presentation of a sensory stimulus
_cortical EEG that follows a sensory stimulus has two components
_the response to the stimulus (signal) – interest part
_the ongoing background EEG activity (the noise) – not interest part (we should NOT care about this part)
_a method used to reduce the noise of the background EGG is signal averaging
_average evoked potentials (AEPs) focuses on the various waves averaged signal. Each wave is characterized by its direction , positive or negative, and by its latency
_small waves that happen in the first few millisecond of the evoked potential do not count because they originate far away in the sensory nuclei of the brain stem – called far-field potentials
