Excitatory weight

In the Mexican Hat function (Figure 3.20), the weights of the winning node and its close neighbors are adjusted to increase their resemblance to the sample pattern (an excitatory effect), but the weights of nodes that are... 

An overview of some of the processes involved in synaptic transmission is shown in Figure 10-1. Many of the processes are discussed below or in other chapters of this book. Many different types of substance are neurotransmitters. Classical neurotransmitters, such as ACh (see Ch. 11) and norepinephrine (NE see Ch. 12), are low-molecular-weight substances that have no other function but to serve as neurotransmitters. The predominant excitatory neurotransmitter in the brain, glutamate, and the inhibitory neurotransmitter in the spinal cord, glycine, are common and essential amino acids (see Chs 15 and 16). 

Although the MAOIs can have serious and potentially life-threatening adverse effects, it is the more common and less dramatic side effects that often lead to the discontinuation of MAOIs. These side effects include orthostatic hypotension, drowsiness, insomnia, edema, weight gain, sexual dysfunction, and precipitation of mania. Rare side effects include hepatitis and leukopenia. Parasthesias may develop secondary to a MAOI-induced pyridoxine deficiency, which responds to oral pyridoxine supplementation. Overall, phenelzine appears to be more sedating, whereas trancylpromine is more activating because of its stimulant-like properties. Meclobomide has more excitatory side effects, such as restlessness and insomnia. 

Inputs most often are a collection of feature nodes that describe a stimulus to which the model will react. These feature nodes are typically assigned values of 1 if they are present and 0 if absent. In the simplest models, input nodes are connected directly to a set of output nodes. Connections exist between every input node and every output node, and each connection carries a weight that reflects the strength of the connection. Connection weights are positive (i.e., excitatory) or negative (i.e., inhibitory). Given a particular input, the input nodes having positive value (i.e., those that represent features which are present in the input) influence the... 

Each of the units has multiple inputs, which may be partly excitatory and partly inhibitory. The units usually obtain a weighted sum of all the inputs, which, as a single output, is passed down the axon analogue elements. The output scalar compares to the average spike rate of a neuron (Crick, 1989). 

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