A century of imagery research: reflections on Cheves Perky's contribution to our understanding of mental imagery

Examining tensions in the past and present uses of concepts

Examining tensions between the past and present uses of scientific concepts can help clarify their contributions as tools in experimental practices. This point can be illustrated by considering the concepts of mental imagery and hallucinations: despite debates over their respective referential reliabilities remaining unresolved within their interdependent histories, both are used as independently stable concepts in neuroimaging experiments. Building on an account of how these concepts function as tools structured for pursuit of diverging goals in experiments, this paper explores this tension by re-examining the continued reliance of each concept on inverse characterisations inherited from the nominally-discarded 'mediator-view' of sensory-like mental phenomena (SLMP). In doing so, I seek to demonstrate how examining unresolved tensions can help highlight that entrenched associations can remain both integral to, and obscured by, the uses of concepts as goal-directed tools within experimental practices.

The Perky effect revisited: Imagery hinders perception at high levels, but aids it at low

Visual, although not auditory, imagery typically interferes with visual acuity: the so-called Perky effect. However, visual images can facilitate detection of visual Gabor patterns. Here we report that this discrepancy is not due so much to the class of stimuli but primarily to the level of accuracy; visual imagery interferes with acuity when performance is good but facilitates it when performance is poor. This finding is analogous to the 'dipper' function obtained when visual stimuli that mask visual targets when above threshold improve target detection near threshold.

Repetition priming results in sensitivity attenuation

Repetition priming refers to the change in the ability to perform a task on a stimulus as a consequence of a former encounter with that very same item. Usually, repetition results in faster and more accurate performance. In the present study, we used a contrast discrimination protocol to assess perceptual sensitivity and response bias of Gabor gratings that are either repeated (same orientation) or alternated (different orientation). We observed that contrast discrimination performance is worse, not better, for repeated than for alternated stimuli. In a second experiment, we varied the probability of stimulus repetition, thus testing whether the repetition effect is due to bottom-up or top-down factors. We found that it is top-down expectation that determines the effect. We discuss the implication of these findings for repetition priming and related phenomena as sensory attenuation. This article is part of a Special Issue entitled SI: Prediction and Attention.

Oscillatory brain activity in the alpha range is modulated by the content of word-prompted mental imagery

Mental imagery is a fundamental cognitive process of interest to basic scientists and clinical researchers. This study examined large-scale oscillatory brain activity in the alpha band (8-12 Hz) during language-driven mental imagery using dense-array EEG. Three experiments demonstrated relative increases in alpha amplitude: (1) during imagery prompted by words compared to fixation without imagery instruction, (2) during imagery of word content compared to imagery of geometric shapes, and (3) during imagery of emotionally evocative words compared to imagery of less emotionally arousing content. Alpha increases for semantically loaded imagery were observed in parieto-occipital regions, sustained throughout the imagery period. Findings imply that alpha oscillations index active memory and internal cognitive processing, reflecting neural communication in cortical networks representing motor, semantic, and perceptual aspects of the imagined scene.

Dissecting perception and memory-driven imagery by boosting GABA-ergic neurotransmission

Flanking lateral masks enhance or weaken the detection of a low-contrast visual target. This effect depends on the target-to-mask distance. An improvement of stimulus detection can also be observed when participants imagine (i.e., retrieve from memory) the previously presented masks. In this double-blind, placebo-controlled study, we show that the gamma-aminobutyric acid-A (GABAA) receptor agonist alprazolam disrupts perceptual but not imagery enhancement of contrast detection in individuals with generalized anxiety and adjustment disorder. The weakened target detection at short target-to-mask distances became more pronounced after the administration of the GABA-agonist in both perception and imagery conditions. Healthy control participants did not differ from individuals with generalized anxiety and adjustment disorder receiving placebo. These results indicate that perception and imagery can be dissociated by boosting GABA-ergic neurotransmission. Further studies are warranted to investigate this effect in healthy individuals.