Theta activity (~ 6-10 Hz) is prevalent throughout the brain including the hippocampus, the neocortex, and the cerebellum (Berry and Thompson 1976, 1978; Dwarakanath, Logothetis et al. 2023; Hoffmann and Berry 2009; Jutras and Buffalo 2010; Lega et al. 2012; Lubenov and Siapas 2009; Siapas and Wilson 1998; Vanderwolf 1969, 1990; Wikgren et al. 2010; Zhang and Jacobs 2015) and it has been associated with volitional acts (Tehovnik 2017; Vanderwolf 1969): walking, running, swimming, speaking, learning new tasks, and so on (but not with immobility, eating, drinking, or grooming, i.e., reflexive behaviors). We have argued that separating declarative memory from procedural memory and attributing the former to the neocortex and the latter to the cerebellum prevents a complete understanding of how the brain learns and stores information (Tehovnik, Hasanbegović, Chen 2024). Learning requires that the declarative and procedural processes co-occur, since it is declarative, consciousness via the neocortex that triggers procedures expressed as sequences of body movements whether during new learning or during bouts of automaticity (Chen and Wise 1995ab; Evarts 1966; Lehericy et al. 2005; Libet 1985; Schiller and Tehovnik 2015; Thach et al. 1992; Vanderwolf 2007). Significantly, if the neocortex is ablated in animals including humans, this causes great difficulty in generating sequences of behavior along with having massive sensory deficits yielding complete ‘blindness’ of a sensory attribute when a primary sensory area (V1, A1, or S1, and so on) is destroyed (Arnts et al. 2020; Kimura 1993; Merker 2007; Pavlov 1927; Tehovnik, Hasanbegović, Chen 2024; Tehovnik, Patel, Tolias et al. 2021; Vanderwolf 2007).
The work of Dwarakanath, Logothetis et al. (2023) suggests that transitions in the thought process (as studied using binocular rivalry) is preceded by a burst of theta activity. During such transitions the ocular movements generated by a subject are altered as well. For example, if horizontally-oriented black and white bars are presented to each eye such that one eye is presented with upward motion of the bars and the other eye is presented with downward motion of the bars, then once a unitary percept is experienced both eyes track the stimulus in the direction of the perception. Thus, thinking and movement coincide, since both processes operate in parallel even if the execution of one’s thoughts in the form of movement is in the future (James 1890; also see Sacks 1976, 2012). A travelling theta-wave along the posterior-anterior axis of the hippocampus has been described in both rodents and primates performing a behavioral task in sequence (Lubenov and Siapas 2009; Zhang and Jacobs 2015). A similar wave must occur once a stream of consciousness is produced without interruption (Dwarakanath, Logothetis et al. 2023; James 1890). So, how many wave cycles would be necessary to deliver a speech without interruption?
During the generation of volitional acts such as walking, running, swimming, and so on (which are accompanied by theta activity), the pathway between the inferior olive and the cerebellar Purkinje neurons is disabled (Apps 1999; Armstrong et al. 1988; Carli et al. 1967; Gellman et al. 1985; Smith and Chapin 1996), which means the efference-copy code cannot be altered at this time. Instead, alterations must occur between pauses/transitions in behavior (during large-amplitude irregular activity of neocortex, Vanderwolf 1969). Behavioral transitions are correlated with a preponderance or an absence of complex spikes about some baseline discharge (Catz, Their et al. 2005; Hasanbegović 2024; Gilbert and Thach 1977; Sendhilnathan, Goldberg et al. 2020; Swain et al. 2011; Yang and Lisberger 2014). It is noteworthy that once task performance is automated, the change in complex spike activity during state transitions is diminished (Swain et al. 2011). The disablement of the inferior olive is believed to be under neocortical control (Apps 1999), and activation of this pathway may occur mainly during immobility or virtual immobility (see Bush et al. 2017) and perhaps during slow-wave sleep as well (Canto, De Zeeuw et al. 2017; Gomperts et al. 2015; Logothetis et al. 2012; Marr 1971; Ólafsdóttir et al. 2017; Pavlides and Winson 1989; Wilson and McNaughton 1994; Yu et al. 2017). Indeed, there is evidence that complex spikes may be present during slow-wave sleep (Canto, De Zeeuw et al. 2023).
In conclusion, theta activity (which is believed to originate in the septum, Buzsáki 2006) occurs throughout the brain, and it includes structures involved in the consolidation and retrieval of information (i.e., the hippocampus, the neocortex, and the cerebellum), and it mediates both the execution of thought and movement, two processes that must be studied as one (James 1890). Changes to complex spike discharge, which have been implicated in altering the efference-copy code (Tehovnik, Hasanbegović, Chen 2024), is more prevalent outside the generation of theta.
Hi,
Theta activity likely signals transitions between events or behaviours. Complex spikes (occurring outside theta activity) may then trigger modifications to the efference copy (our internal model of how our actions affect the world).
Just my thought.
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