Figure 2.6 Synapses (Part 1)

EM of synapses on cell body

Postsynaptic potentials Postsynaptic potentials are brief changes in the resting potential at a synapse –Excitatory postsynaptic potential (EPSP) – produces a small local depolarization, pushing the cell closer to threshold –Inhibitory postsynaptic potential (IPSP) – produces a small hyperpolarization, pushing the cell further away from threshold EPSP can result from sodium ions (Na+) entering the cell, making the inside more negative. IPSP can result from chloride ions (Cl - ) entering the cell, making the inside more negative.

Fig 3.9 Recording Postsynaptic Potentials

Figure 3.10 Integration of Excitatory and Inhibitory Inputs

Spatial and Temporal summation Spatial summation –summing of Postsynaptic potentials arriving at different parts of the cell. Temporal summation –summing of Postsynaptic potentials that arrive at different times The integration of EPSPs and IPSPs –at the axon hillock –Determines if an action potential will occur

Figure 3.11 Spatial Versus Temporal Summation (Part 2)

Anatomical Types of Synapses Figure 11.17

You Tube video animations –Neuron Synapse: EPSP and IPSPNeuron Synapse: EPSP and IPSP –Neural Communication: EPSP and IPSPNeural Communication: EPSP and IPSP Spatial and Temporal Summation

Gross Electrical Activity of the Human Brain An electroencephalogram (EEG) is a recording of brain potentials, or brain waves. –patterns of activity from large areas combination of spatial and temporal summation Used in both clinical and experimental settings –study sleep states –processing in auditory circuit “event-related potentials” (ERP) –seizure disorders

Fig 3.16a EEG recording

Epilepsy Characterized by a synchronization of electrical activity during seizure as described as epileptiform –Grand mal – (Tonic-clonic) abnormal activity throughout the brain movements are tonic and clonic contractions Seizure is followed by confusion and sleep. –Petit mal seizure – (Absence) seizure activity for 5 to 15 seconds No unusual muscle activity Events during seizure are not remembered. –Complex partial seizures do not involve entire brain Wide variety of symptoms Aura – unusual sensation that may precede a seizure Causes of Epilepsy –Head injury from trauma, stroke, tumors or infection –Developmental: anatomical, channelopathy –Abnormal levels of ions “Na” or blood glucose

Figure 3.20 Discharge Patterns during Seizures

Basic mechanisms of epilepsy Mechanisms in chronically epileptic tissue –Increased synaptic connectivity mossy fiber sprouting –Channelopathies (see Box 3.1) potassium channels are weakened sodium channels are more persistent weak GABA receptor activation –alterations in expression of receptors

Figure 3.21 Event-Related Potentials

Emotional Processing, P50 Sensory Gating, and Social Functioning in Bipolar Disorder sensory gating is modified by emotional processing use event-related potential to measure sensory gating Individuals with bipolar disorder –emotional processing can be either to high or to low Test emotional processing effects on sensory gating –in individuals with bipolar disorder –Paired click paradigm “auditory” stimulus 1 followed by stimulus 2 Present either a disgusting facial expression or a neutral faces Bipolar Disorder causes impaired filtering of auditory information when paired with an emotionally salient image “disgusting facial expression”