RESUMEN
Our eyes do not only respond to visual perception but also to internal cognition involving visual imagery, which can be referred to as internal coupling. This review synthesizes evidence on internal coupling across diverse domains including episodic memory and simulation, visuospatial memory, numerical cognition, object movement, body movement, and brightness imagery. In each domain, eye movements consistently reflect distinct aspects of mental imagery typically akin to those seen in corresponding visual experiences. Several findings further suggest that internal coupling may not only coincide with but also supports internal cognition as evidenced by improved cognitive performance. Available theoretical accounts suggest that internal coupling may serve at least two functional roles in visual imagery: facilitating memory reconstruction and indicating shifts in internal attention. Moreover, recent insights into the neurobiology of internal coupling highlight substantially shared neural pathways in externally and internally directed cognition. The review concludes by identifying open questions and promising avenues for future research such as exploring moderating roles of context and individual differences in internal coupling.
Asunto(s)
Movimientos Oculares , Imaginación , Percepción Visual , Humanos , Percepción Visual/fisiología , Imaginación/fisiología , Movimientos Oculares/fisiología , Cognición/fisiología , Atención/fisiologíaRESUMEN
Eyes are active in memory recall and visual imagination, yet our grasp of the underlying qualities and factors of these internally coupled eye movements is limited. To explore this, we studied 50 participants, examining how workload, spatial reference availability, and imagined movement direction influence internal coupling of eye movements. We designed a visuospatial working memory task in which participants mentally moved a black patch along a path within a matrix and each trial involved one step along this path (presented via speakers: up, down, left, or right). We varied workload by adjusting matrix size (3 × 3 vs. 5 × 5), manipulated availability of a spatial frame of reference by presenting either a blank screen (requiring participants to rely solely on their mental representation of the matrix) or spatial reference in the form of an empty matrix, and contrasted active task performance to two control conditions involving only active or passive listening. Our findings show that eye movements consistently matched the imagined movement of the patch in the matrix, not driven solely by auditory or semantic cues. While workload influenced pupil diameter, perceived demand, and performance, it had no observable impact on internal coupling. The availability of spatial reference enhanced coupling of eye movements, leading more frequent, precise, and resilient saccades against noise and bias. The absence of workload effects on coupled saccades in our study, in combination with the relatively high degree of coupling observed even in the invisible matrix condition, indicates that eye movements align with shifts in attention across both visually and internally represented information. This suggests that coupled eye movements are not merely strategic efforts to reduce workload, but rather a natural response to where attention is directed.
Asunto(s)
Movimientos Oculares , Memoria a Corto Plazo , Percepción Espacial , Humanos , Memoria a Corto Plazo/fisiología , Adulto , Masculino , Femenino , Adulto Joven , Percepción Espacial/fisiología , Movimientos Oculares/fisiología , Imaginación/fisiología , Percepción Visual/fisiología , Desempeño Psicomotor/fisiologíaRESUMEN
Cilia and flagella often exhibit synchronized behavior; this includes phase locking, as seen in Chlamydomonas, and metachronal wave formation in the respiratory cilia of higher organisms. Since the observations by Gray and Rothschild of phase synchrony of nearby swimming spermatozoa, it has been a working hypothesis that synchrony arises from hydrodynamic interactions between beating filaments. Recent work on the dynamics of physically separated pairs of flagella isolated from the multicellular alga Volvox has shown that hydrodynamic coupling alone is sufficient to produce synchrony. However, the situation is more complex in unicellular organisms bearing few flagella. We show that flagella of Chlamydomonas mutants deficient in filamentary connections between basal bodies display markedly different synchronization from the wild type. We perform micromanipulation on configurations of flagella and conclude that a mechanism, internal to the cell, must provide an additional flagellar coupling. In naturally occurring species with 4, 8, or even 16 flagella, we find diverse symmetries of basal body positioning and of the flagellar apparatus that are coincident with specific gaits of flagellar actuation, suggesting that it is a competition between intracellular coupling and hydrodynamic interactions that ultimately determines the precise form of flagellar coordination in unicellular algae.