Neuroscience Lecture 4 2024.pdf

Neuroscience Lecture 4 How we study the brain (Research methods in behavioural & cognitive neuroscience) (Carlson pp 101-106)  Mapping the functional organisation of the brain: Studying effects of experimental brain lesions in animals...

Neuroscience Lecture 4 How we study the brain (Research methods in behavioural & cognitive neuroscience) (Carlson pp 101-106)  Mapping the functional organisation of the brain: Studying effects of experimental brain lesions in animals and accidental brain lesions in humans 2  Transcranial Magnetic Stimulation (TMS) Magnetic pulse electrical current in brain depolarises neurons (Action Potentials). 3  Single-cell recording / Electrical stimulation LR Hochberg et al. Nature 485, 372-375 (2012) doi:10.1038/nature11076 Optogenetics and fibre-photometry (Ca++ imaging) Microinjection into specific region of brain. 4  Functional Imaging of the Human Brain Measuring which brain areas become active when. Electroencephalography (EEG) Functional Magnetic Resonance Imaging (fMRI) Magnetoencephalography (MEG) Correlations between brain activity and psychological function. Doesn’t prove causal link. (vs TMS) 5  EEG Electrode plates against scalp record electrical fields from brain Very good temporal resolution: (~ 20 ms); poor spatial resolution (not good for seeing exactly where activity occurred).  Magnetic Resonance Imaging (MRI) Bombarding head with high frequency radio waves, while inside a strong magnetic field, to measure orientation of protons (in water). This identifies different types of brain tissue, to allow visualisation of brain structures. 7 Functional Magnetic Resonance Imaging (fMRI) fMRI measures changes in O2 in blood (differences in the magnetic properties of O2-rich and O2-depleted blood: “BOLD” response). fMRI has good spatial resolution, especially when combined with high-quality anatomical MRI. But BOLD response lags behind actual brain activity, and temporal resolution not so high. 8 Magnetoencephalography (MEG) measures magnetic fields emitted from brain. 3D reconstruction of electrical activity to create functional map of brain response. 9  Magnetoencephalography (MEG) Excellent temporal resolution (equal to EEG) and good spatial resolution, and completely non-invasive. But equipment is hugely expensive, and extremely sensitive to any source of electromagnetic interference (eg, from any electrical device). 10  The Regulation of Feeding Hunger and satiety triggered by contents of stomach and substances circulating in blood (sugars, fats, hormones). But BRAIN is responsible for the subjective experience of hunger/satiety and behavioural response (find food/ stop eating). Hypothalamus very important:  Hypothalamus PVN PVN LH LH VMH VMH Arc 14  Hypothalamus Lateral Hypothalamus: Destruction of LH causes rats to LH reduce eating LH dramatically 15  Hypothalamus Lateral Hypothalamus: Destruction of LH causes rats to LH reduce eating LH dramatically VMH VMH Ventromedial Hypothalamus: Destruction of VMH makes rats overeat. But not lack satiety: meals normal size, 16 but more frequent  Hypothalamus Lateral Hypothalamus: PVN PVN Paraventricular Destruction of nucleus: LH causes rats to LH Rats with damage reduce eating LH to PVN eat dramatically BIGGER meals. VMH VMH Ventromedial Hypothalamus: Destruction of VMH makes rats overeat. But not lack satiety: meals normal size, but more frequent 17  Hypothalamus Lateral Hypothalamus: PVN PVN Paraventricular Destruction of nucleus: LH causes rats to LH Rats with damage reduce eating LH to PVN eat dramatically BIGGER meals. VMH VMH + Arc - Arcuate Nucleus (Arc) contains 2 types of neurons: 1) promote feeding (via LH) and 2) suppress feeding (via VMH & PVN): Ventromedial Hypothalamus: fasting/feeding can activate each class; Destruction of VMH makes stimulation can induce/stop feeding. rats overeat. But not lack satiety: meals normal size, but more frequent 18  Hypothalamus Lateral Hypothalamus: PVN PVN Paraventricular Destruction of nucleus: LH causes rats to LH Rats with damage reduce eating LH to PVN eat dramatically BIGGER meals. VMH VMH + Arc - Arcuate Nucleus (Arc) contains 2 types of neurons: 1) promote feeding (via LH) and 2) suppress feeding (via VMH & PVN): Ventromedial Hypothalamus: fasting/feeding can activate each class; Destruction of VMH makes stimulation can induce/stop feeding. rats overeat. Arc has “leaky” BBB, and neurons have But not lack satiety: receptors for hormones from gut meals normal size, (ghrelin, insulin) and fat (leptin) and. but more frequent 19