Date of oral examination:iii * This and the following sections will be largely focused, with very few exceptions, on the analysis of oscillatory activity reported from extra cellular recordings (local field potentials (LFP) and multi-unitactivity (MUA)) in mammals, generally rodents, cats or monkeys. * The distribution of functional roles linked to the theta band over time was presented in 47 , more than thirty roles were linked to the rhythm in the 1960s * The quote continues: " There is no direct proof that synchrony leads to changes in behavior when it is selectively altered. Such direct evidence has only been obtained in the olfactory system of insects. Stopfer et al 240 showed that odor discrimination deteriorates if synchronization patterns among olfactory bulb cells are disturbed. The search for similar evidence in the vertebrate brain is a daunting challenge, but future studies in this direction are a priority." . * Spike Field coherence as used in 87 , is defined as the power spectrum of the spike-triggered average normalized by the mean power spectrum over the LFP segments used to obtain the STA * Granger Causality measures the reduction of unexplained variance of a process x at time t when considering only the past values compared to when also the past values of a process y are included. Significant Granger Causality is used here and elsewhere as a synonym of causal influence.† FEF having faster responses than V4 was also reported in a feature-attention task, in which no frequency dependence was analyzed 290 * By delta connections it is meant that the input current to a neuron at time t as a consequence of an incoming spike at time t0 is modeled as I ∝ δ(t − t0).† The LIF neuron is defined as τm V = −V + I, where τm is the membrane time constant, V is the voltage and I is a constant input current. For the model to be completed, a threshold Vt and a reset Vr voltage values have as well to be defined. * The QIF neuron, defined as τM V = V 2 + I, will be studied in detail in Chapter 3.† The f-I curve is the dependence of the firing rate of the neuron to an increasing input current. Neurons with a Type I neuronal excitability 122 as the one studied here, can achieve arbitrarily low firing rates * They also studied the dynamics in the vicinity of the instability and provided analytical expressions for corrections to the oscillation frequency. * GABA A mediates fast inhibition.† AMPA is a glutamate receptor mediating fast excitation. * The number of connections K is much smaller than the number of neurons N † The number of connections K is no longer required to be much smaller than N * The first Lyapunov exponent is the rate of divergence of two trajectories as a consequence of an infinitesimal perturbation. Rigorous definitions will be given in the Methods of Chapter 3. * Generally, when referring to balanced state networks, the following is assumed: N neurons are connected with on average K other neurons, and the weight of the connections J scales like 1/ √ K * As opposed to the stable dynamics shown for t...