In Search of Oscillatory Traces of the Internal Clock

Neural oscillations are ubiquitous in the mammalian brain and they are typically classified according to their specific frequency responses (Buzsáki, 2006). Neural oscillations are hypothesized to organize communication within and between brain networks (e.g., Fries, 2015). Neural oscillations have increasingly been associated with various cognitive functions such as One quest in cognitive neuroscience is to explain how neural oscillations can subserve complex cognitive processes. Here, we mainly focus on the role of spontaneous rhythms in interval timing (also see van Wassenhove, in press); however, some hypotheses are supported by the literature on rhythmic entrainment. One of the possible cognitive abilities neural oscillations may support is interval timing (Treisman et al., 1994), which is the ability to perceive, store, encode, and reproduce temporal intervals ranging from few 100 milliseconds to minutes. Over decades, experimental psychologists have proposed the existence of a cognitive mechanism akin to an internal clock. In search for the neural bases of the internal clock(s), it may be tempting to draw an analogy between ticking clocks and oscillating neuronal networks, as one of the reference papers in neurosciences states, " Clocks tick, bridges, and skyscrapers vibrate, neuronal networks oscillate " (Buzsáki and Draguhn, 2004, pp. 1926). Indeed, some interval timing theories have followed through this idea: Treisman (1963) suggested, that the internal clock could consist of a pacemaker which at the beginning of the to-be-timed interval would start sending pulses, that are then stored in the accumulator. The pulse count could serve as a subjective estimate of time. Furthermore, to implement this model into biologically plausible mechanisms, Treisman proposed that the pulse rate of the pacemaker would be driven by neural oscillations in the alpha range (8–12 Hz, see Figure 1A): faster alpha rhythms would thus result in longer estimates of time than slower alpha rhythms considering, that more pulses would accumulate during the same physical time interval (Treisman et al., 1994). As no simple relationships have been found between the rate of visual flicker, neural oscillations, and the subjective perception of duration when using oscillatory entrainment (Herbst et al., 2013, 2014; although see Johnston et al., 2006), it remains plausible that spontaneous fluctuations of alpha peaks could modulate perceived duration. For example, Haegens et al. (2014) have shown, that alpha peak frequency changed as a function of cognitive load in a N-back working memory (WM) task such that the larger the WM load, the higher the alpha …