Receiving reviews of a paper (Tehovnik, Carvey et al. 2003) in which we electrically stimulated the visual cortex of primates to evoke saccadic eye movements under various behavioral conditions to be told by a reviewer that we needed to change the term ‘behavioral state’ to ‘attention’—even if the variable under study was the time of juice delivery which has little to do with attention. Many neuroscientists have made it their mission to determine how the neocortex subserves attention. John Maunsell just published a paper in which he and colleagues stimulated the nucleus coeruleus, which dilates the pupils and which was reported to enhance ‘attentional effects’ for visual stimuli falling in the receptive field of visual cortical neurons as monkeys fixated a central spot (Ghosh and Maunsell 2024). When primates fixate objects of interest they adjust their pupil size to establish an optimal depth of field (Chen et al. 2016; Suryakumar and Allison 2015), so by activating the nucleus coeruleus (which has nothing to do with depth of field) they are imposing a state on an animal that would interrupt this process, a process that depends on a titrated alteration (mainly a reduction) in pupil size. Also, although attentional effects (i.e., enhancement of unit firing) are observed when placing visual stimuli in non-foveal parts of the visual field, most vision in primates is mediated by the fovea (Schiller and Tehovnik 2015). Case in point, a person that has foveal damage finds it almost impossible to read text with the peripheral visual field (Chung 2011). No amount of ‘attention’ can fix this.
When human subjects are engaged in volitional behaviors such as reading, talking, walking, or running, an efference-copy signal of the motor command is believed to be sent to the auditory cortex with the purpose of suppressing auditory neurons (Nelson, Mooney et al. 2013; Tehovnik 2017). As many in the oculomotor and skeletomotor fields understand, efference-copy control allows an animal to focus on its ongoing behavioral state, whether it is related to ‘peripheral field’ visual attention or some other sensorimotor condition. For example, when electric fishes communicate with conspecifics using electrical pulses, an efference copy signal is passed through the cerebellum so that the communicating fish does not confuse its message with those originating from conspecifics (Fukutomi and Carlson 2020). A similar process is in play when primates engage in self-motion to discriminate this motion from externally-induced motion of the body (Cullen 2015).
We believe that once cerebellar control of the efference copy signal is understood with respect to the neocortex that studies specifically related to attending to peripherally located visual targets will become one item of many to be put under study. In fact, Goldberg and colleagues (Duhamel, Goldberg et al. 1992; Sommer and Wurtz 2006) have avoided studies in the cerebellum as it pertains to their remapping signal, even though they believe this signal represents a corollary discharge (Fukutomi and Carlson 2020; Rao et al. 2016). Furthermore, it is suspected by many that their signal is really one that directs the fovea to fixate visual targets of interest rather than to focus an animal’s attention on items falling in the peripheral visual field (cf., Tolias et al. 2001; Zirnsak et al. 2014 vs. Duhamel, Goldberg et al. 1992; Sommer and Wurtz 2006).
To reiterate, just how the cerebellum communicates with the neocortex for the establishment of efference-copy signals needs further study for all behaviors that require discriminating between self-motion and externally-induced body movement. Such an effort is ongoing (Bell et al. 1997; Chen 2019; Cullen 2015; De Zeeuw 2021; Fukutomi and Carlson 2020; Guell, Schmahmann et al. 2018; Loyola et al. 2019; Miles and Lisberger 1981; Noda et al. 1991; Shadmehr 2020; Tehovnik, Patel, Tolias et al. 2021; Wang et al. 2023).
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