Slower but more accurate mental rotation performance in aphantasia linked to differences in cognitive strategies

Mental rotation tasks are frequently used as standard measures of mental imagery. However, aphantasia research has brought such use into question. Here, we assessed a large group of individuals who lack visual imagery (aphantasia) on two mental rotation tasks: a three-dimensional block-shape, and a human manikin rotation task. In both tasks, those with aphantasia had slower, but more accurate responses than controls. Both groups demonstrated classic linear increases in response time and error-rate as functions of angular disparity. In the three-dimensional block-shape rotation task, a within-group speed-accuracy trade-off was found in controls, whereas faster individuals in the aphantasia group were also more accurate. Control participants generally favoured using object-based mental rotation strategies, whereas those with aphantasia favoured analytic strategies. These results suggest that visual imagery is not crucial for successful performance in classical mental rotation tasks, as alternative strategies can be effectively utilised in the absence of holistic mental representations.

Revisiting the blind mind: Still no evidence for sensory visual imagery in individuals with aphantasia

The inability to visualise was given the name aphantasia in 2015 by Zeman and colleagues. In 2018 we published research showing that fifteen individuals who self-identified as having aphantasia also demonstrated a lack of sensory visual imagery when undergoing the binocular rivalry imagery paradigm, suggesting more than just a metacognitive difference. Here we update these findings with over fifty participants with aphantasia and show that there is evidence for a lack of sensory imagery in aphantasia. How the binocular rivalry paradigm scores relate to the vividness of visual imagery questionnaire (VVIQ) and how aphantasia can be confirmed is discussed.

Reality check: how do we know what's real?

How do we know what is real and what is merely a figment of our imagination? Dijkstra and Fleming tackle this question in a recent study. In contrast to the classic Perky effect, they found that once imagery crosses a 'reality threshold', it becomes difficult to distinguish from reality.

Multisensory subtypes of aphantasia: Mental imagery as supramodal perception in reverse

Cognitive neuroscience research on mental imagery has largely focused on the visual imagery modality in unimodal task contexts. Recent studies have uncovered striking individual differences in visual imagery capacity, with some individuals reporting a subjective absence of conscious visual imagery ability altogether ("aphantasia"). However, naturalistic mental imagery is often multi-sensory, and preliminary findings suggest that many individuals with aphantasia also report a subjective lack of mental imagery in other sensory domains (such as auditory or olfactory imagery). In this paper, we perform a series of cluster analyses on the multi-sensory imagery questionnaire scores of two large groups of aphantasic subjects, defining latent sub-groups in this sample population. We demonstrate that aphantasia is a heterogenous phenomenon characterised by dominant sub-groups of individuals with visual aphantasia (those who report selective visual imagery absence) and multi-sensory aphantasia (those who report an inability to generate conscious mental imagery in any sensory modality). We replicate our findings in a second large sample and show that more unique aphantasia sub-types also exist, such as individuals with selectively preserved mental imagery in only one sensory modality (e.g. intact auditory imagery). We outline the implications of our findings for network theories of mental imagery, discussing how unique aphantasia aetiologies with distinct self-report patterns might reveal alterations to various levels of the sensory processing hierarchy implicated in mental imagery.

Memories with a blind mind: Remembering the past and imagining the future with aphantasia

Our capacity to re-experience the past and simulate the future is thought to depend heavily on visual imagery, which allows us to construct complex sensory representations in the absence of sensory stimulation. There are large individual differences in visual imagery ability, but their impact on autobiographical memory and future prospection remains poorly understood. Research in this field assumes the normative use of visual imagery as a cognitive tool to simulate the past and future, however some individuals lack the ability to visualise altogether (a condition termed "aphantasia"). Aphantasia represents a rare and naturally occurring knock-out model for examining the role of visual imagery in episodic memory recall. Here, we assessed individuals with aphantasia on an adapted form of the Autobiographical Interview, a behavioural measure of the specificity and richness of episodic details underpinning the memory of events. Aphantasic participants generated significantly fewer episodic details than controls for both past and future events. This effect was most pronounced for novel future events, driven by selective reductions in visual detail retrieval, accompanied by comparatively reduced ratings of the phenomenological richness of simulated events, and paralleled by quantitative linguistic markers of reduced perceptual language use in aphantasic participants compared to those with visual imagery. Our findings represent the first systematic evidence (using combined objective and subjective data streams) that aphantasia is associated with a diminished ability to re-experience the past and simulate the future, indicating that visual imagery is an important cognitive tool for the dynamic retrieval and recombination of episodic details during mental simulation.

The pupillary light response as a physiological index of aphantasia, sensory and phenomenological imagery strength

The pupillary light response is an important automatic physiological response which optimizes light reaching the retina. Recent work has shown that the pupil also adjusts in response to illusory brightness and a range of cognitive functions, however, it remains unclear what exactly drives these endogenous changes. Here, we show that the imagery pupillary light response correlates with objective measures of sensory imagery strength. Further, the trial-by-trial phenomenological vividness of visual imagery is tracked by the imagery pupillary light response. We also demonstrated that a group of individuals without visual imagery (aphantasia) do not show any significant evidence of an imagery pupillary light response, however they do show perceptual pupil light responses and pupil dilation with larger cognitive load. Our results provide evidence that the pupillary light response indexes the sensory strength of visual imagery. This work also provides the first physiological validation of aphantasia.

Visual working memory in aphantasia: Retained accuracy and capacity with a different strategy

Visual working memory paradigms involve retaining and manipulating visual information in mind over a period of seconds. Evidence suggests that visual imagery (sensory recruitment) is a strategy used by many to retain visual information during such tasks, leading some researchers to propose that visual imagery and visual working memory may be one and the same. If visual imagery is essential to visual working memory task performance there should be large ramifications for a special population of individuals who do not experience visual imagery, aphantasia. Here we assessed visual working memory task performance in this population using a number of different lab and clinical working memory tasks. We found no differences in capacity limits for visual, general number or spatial working memory for aphantasic individuals compared to controls. Further, aphantasic individuals showed no significant differences in performance on visual components of clinical working memory tests as compared to verbal components. However, there were significant differences in the reported strategies used by aphantasic individuals across all memory tasks. Additionally, aphantasic individual's visual memory accuracy did not demonstrate a significant oblique orientation effect, which is proposed to occur due to sensory recruitment, further supporting their non-visual imagery strategy reports. Taken together these data demonstrate that aphantasic individuals are not impaired on visual working memory tasks, suggesting visual imagery and working memory are not one and the same, with imagery (and sensory recruitment) being just one of the tools that can be used to solve visual working memory tasks.

The critical role of mental imagery in human emotion: insights from fear-based imagery and aphantasia

One proposed function of imagery is to make thoughts more emotionally evocative through sensory simulation, which can be helpful both in planning for future events and in remembering the past, but also a hindrance when thoughts become overwhelming and maladaptive, such as in anxiety disorders. Here, we report a novel test of this theory using a special population with no visual imagery: aphantasia. After using multi-method verification of aphantasia, we show that this condition, but not the general population, is associated with a flat-line physiological response (skin conductance levels) to reading and imagining frightening stories. Importantly, we show in a second experiment that this difference in physiological responses to fear-inducing stimuli is not found when perceptually viewing fearful images. These data demonstrate that the aphantasic individuals' lack of a physiological response when imaging scenarios is likely to be driven by their inability to visualize and is not due to a general emotional or physiological dampening. This work provides evidence that a lack of visual imagery results in a dampened emotional response when reading fearful scenarios, providing evidence for the emotional amplification theory of visual imagery.

Attention driven phantom vision: measuring the sensory strength of attentional templates and their relation to visual mental imagery and aphantasia

When we search for an object in an array or anticipate attending to a future object, we create an 'attentional template' of the object. The definitions of attentional templates and visual imagery share many similarities as well as many of the same neural characteristics. However, the phenomenology of these attentional templates and their neural similarities to visual imagery and perception are rarely, if ever discussed. Here, we investigate the relationship between these two forms of non-retinal phantom vision through the use of the binocular rivalry technique, which allows us to measure the sensory strength of attentional templates in the absence of concurrent perceptual stimuli. We find that attentional templates correlate with both feature-based attention and visual imagery. Attentional templates, like imagery, were significantly disrupted by the presence of irrelevant visual stimuli, while feature-based attention was not. We also found that a special population who lack the ability to visualize (aphantasia), showed evidence of feature-based attention when measured using the binocular rivalry paradigm, but not attentional templates. Taken together, these data suggest functional similarities between attentional templates and visual imagery, advancing the theory of visual imagery as a general simulation tool used across cognition. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Hallucinations on demand: the utility of experimentally induced phenomena in hallucination research

Despite the desire to delve deeper into hallucinations of all types, methodological obstacles have frustrated development of more rigorous quantitative experimental techniques, thereby hampering research progress. Here, we discuss these obstacles and, with reference to visual phenomena, argue that experimentally induced phenomena (e.g. hallucinations induced by flickering light and classical conditioning) can bring hallucinations within reach of more objective behavioural and neural measurement. Expanding the scope of hallucination research raises questions about which phenomena qualify as hallucinations, and how to identify phenomena suitable for use as laboratory models of hallucination. Due to the ambiguity inherent in current hallucination definitions, we suggest that the utility of phenomena for use as laboratory hallucination models should be represented on a continuous spectrum, where suitability varies with the degree to which external sensory information constrains conscious experience. We suggest that existing strategies that group pathological hallucinations into meaningful subtypes based on hallucination characteristics (including phenomenology, disorder and neural activity) can guide extrapolation from hallucination models to other hallucinatory phenomena. Using a spectrum of phenomena to guide scientific hallucination research should help unite the historically separate fields of psychophysics, cognitive neuroscience and clinical research to better understand and treat hallucinations, and inform models of consciousness. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Aphantasia: The science of visual imagery extremes

Visual imagery allows us to revisit the appearance of things in their absence and to test out virtual combinations of sensory experience. Visual imagery has been linked to many cognitive processes, such as autobiographical and visual working memory. Imagery also plays symptomatic and mechanistic roles in neurologic and mental disorders and is utilized in treatment. A large network of brain activity spanning frontal, parietal, temporal, and visual cortex is involved in generating and maintain images in mind. The ability to visualize has extreme variations, ranging from completely absent (aphantasia) to photo-like (hyperphantasia). The anatomy and functionality of visual cortex, including primary visual cortex, have been associated with individual differences in visual imagery ability, pointing to a potential correlate for both aphantasia and hyperphantasia. Preliminary evidence suggests that lifelong aphantasia is associated with prosopagnosia and reduction in autobiographical memory; hyperphantasia is associated with synesthesia. Aphantasic individuals can also be highly imaginative and are able to complete many tasks that were previously thought to rely on visual imagery, demonstrating that visualization is only one of many ways of representing things in their absence. The study of extreme imagination reminds us how easily invisible differences can escape detection.

Cortical excitability controls the strength of mental imagery

Mental imagery provides an essential simulation tool for remembering the past and planning the future, with its strength affecting both cognition and mental health. Research suggests that neural activity spanning prefrontal, parietal, temporal, and visual areas supports the generation of mental images. Exactly how this network controls the strength of visual imagery remains unknown. Here, brain imaging and transcranial magnetic phosphene data show that lower resting activity and excitability levels in early visual cortex (V1-V3) predict stronger sensory imagery. Further, electrically decreasing visual cortex excitability using tDCS increases imagery strength, demonstrating a causative role of visual cortex excitability in controlling visual imagery. Together, these data suggest a neurophysiological mechanism of cortical excitability involved in controlling the strength of mental images.

Redefining Visual Working Memory: A Cognitive-Strategy, Brain-Region Approach

The ability to remember and manipulate visual information is pervasive and is associated with many cognitive abilities. Yet despite the importance of visual working memory (VWM), there is little consensus among researchers in the field as to which neural areas are necessary and sufficient and which models best describe its capacity. Here, we propose that an assumption that all people remember visual information in the same way has led to much contention and inconsistencies in the field. By accepting that there are multiple cognitive strategies and methods to perform a VWM task, we introduce an individual “precision” approach to the study of memory. We propose that VWM should be redefined, not by the type of stimuli used (e.g., visual) but rather by the specific mental processes (e.g., visual imagery, semantic, propositional, spatial) and the corresponding brain regions used to complete the mnemonic task. We further provide a short how-to guide for measuring different mnemonic strategies used for working memory.

Imagine that: elevated sensory strength of mental imagery in individuals with Parkinson's disease and visual hallucinations

Visual hallucinations occur when our conscious experience does not accurately reflect external reality. However, these dissociations also regularly occur when we imagine the world around us in the absence of visual stimulation. We used two novel behavioural paradigms to objectively measure visual hallucinations and voluntary mental imagery in 19 individuals with Parkinson's disease (ten with visual hallucinations; nine without) and ten healthy, age-matched controls. We then used this behavioural overlap to interrogate the connectivity both within and between the major attentional control networks using resting-state functional magnetic resonance imaging. Patients with visual hallucinations had elevated mental imagery strength compared with patients without hallucinations and controls. Specifically, the sensory strength of imagery predicted the frequency of visual hallucinations. Together, hallucinations and mental imagery predicted multiple abnormalities in functional connectivity both within and between the attentional control networks, as measured with resting-state functional magnetic resonance imaging. However, the two phenomena were also dissociable at the neural level, with both mental imagery and visual misperceptions associated with specific abnormalities in attentional network connectivity. Our results provide the first evidence of both the shared and unique neural correlates of these two similar, yet distinct phenomena.

Indigenous Health: ACTION on Prevention - 50th annual Australian Society for Medical Research National Scientific Conference

The 50th annual National Scientific Conference of the Australian Society for Medical Research was held in Cairns, Queensland, 13-16 November 2011. The theme, 'Indigenous Health: ACTION on Prevention' highlighted the direct action being undertaken by health and medical researchers, as well as allied health professionals, to improve long-term health outcomes for Indigenous Australians.

315. HOMEOBOX GENES ARE DIFFERENTIALLY EXPRESSED IN PRIMARY VILLOUS AND EXTRAVILLOUS TROPHOBLAST CELL LINEAGES DURING EARLY PREGNANCY

During human placental development trophoblast cells differentiate along either the villous cytotrophoblast (VCT) lineage to form the syncytiotrophoblast (ST) or the invasive extravillous cytotrophoblast (EVCT) lineage (1). Abnormalities in early differentiation processes are characteristic of poor placentation, which is associated with fetal growth restriction (FGR) and pre-eclampsia (PE), the major clinical complications of human pregnancy (2). A large family of homeobox gene transcription factors controls “cell-fate decisions” during development (3), but the expression profile and role of homeobox genes in the human trophoblast cell lineages is not well understood. The aim of the study was to determine homeobox gene expression in primary cultures of mononuclear VCT (2h) and EVCT (2 h) obtained from first trimester human chorionic villi of 8–12 weeks of gestation and in vitro differentiated ST (72 h) and invasive EVCT (48 h), respectively. The isolation and characterization of freshly isolated VCT, EVCT and in vitro differentiated ST and invasive EVCT were performed as described previously (1,4). The homeobox gene mRNA profile was performed using PCR arrays in a pooled sample of VCT and EVCT (n = 6 in each group) and further validated by real-time PCR. Homeobox gene expression studies revealed MSX2 mRNA levels were the highest in VCT (2 h) but undetectable in EVCT (2 h). Further comparisons of homeobox gene expression in in vitro differentiated ST to invasive EVCT showed marked increase in MSX2, DLX3, DLX4 and MEIS1 mRNA levels in ST, which are regulators of cellular differentiation in many studies. Homeobox genes HLX and HHEX, which are implicated in regulating cellular proliferation showed decreased mRNA levels in ST compared to invasive EVCT. Our results demonstrated several known placental and novel homeobox genes are differentially expressed in trophoblast cell lineages. Functional studies of these candidate genes will provide a better understanding of the molecular mechanisms of early placental development. (1) Tarrade et al. (2001) Lab Invest. 81, 1199–1211.(2) LokeYW and King A (1995) Cell Biology and Immunology, Cambridge ed.(3) J Cross et al. (2002) Recent Progress in Hormone Research 57: 221–234.(4) Handschuh et al. (2007) Placenta, 28, 175–184.

The role of protein kinase C in arachidonic acid release and prostaglandin E production from CHO cells transfected with EGF receptors

Arachidonic acid release and prostaglandin production are stimulated by both phorbol esters and growth factors in various cell types. Whereas phorbol esters activate and transmit a signal via protein kinase C, this pathway is not necessarily involved in growth factor signal transduction. We investigated the involvement of protein kinase C in the pathway of arachidonic acid metabolism by CHO cells transfected with full-length EGF receptor (CHOwt). Two isoforms of protein kinase C were identified in CHOwt cells, alpha and zeta. On downregulation, the parallel loss of phorbol ester-stimulated arachidonic acid release and the alpha-isoform suggests a possible involvement of this isoform in phospholipase A2 activation in these cells. In addition, we propose that the zeta-isoform may be separately involved in prostaglandin production as residual phorbol ester-stimulation of PGE production occurs in downregulated cells where PKC zeta is the sole remaining isoform. EGF stimulation of arachidonic acid release, as a measure of phospholipase A2 activation, and subsequent prostaglandin production are unaffected by inhibition of protein kinase C in CHOwt cells. Indeed one such inhibitor, staurosporine, augmented the EGF effect. These results suggest that PKC is not required for EGF activation of phospholipase A2 in these cells.

Sequence of the algL gene of Pseudomonas aeruginosa and purification of its alginate lyase product

The alginate lyase-encoding gene (algL) of Pseudomonas aeruginosa was localized to a 1.7-kb EcoRI-XbaI fragment within the alginate biosynthetic gene cluster at 34 minutes on the chromosome. The nucleotide sequence of this DNA fragment revealed an ORF encoding a protein of M(r) 40,885 which is transcribed in the same orientation as the other alg genes within the biosynthetic gene cluster. The predicted protein has a potential N-terminal signal peptide which is consistent with its proposed periplasmic location. The AlgL protein was overproduced in Escherichia coli and purified. The purified protein was shown to have alginate lyase activity. In addition, an algL insertion mutant of the mucoid P. aeruginosa 8830 was constructed. This mutant (alm1) had a nonmucoid phenotype due to a polar effect on the transcription of an essential alg gene, algA. Thus, the algL gene is located within a region of the alginate biosynthetic gene cluster that appears to be non-essential for alginate production.

Fibronectin-induced increase in mesangial cell prostaglandin release. Effect of hyperglycemia and PKC inhibition

Glomerular accumulation of extracellular matrix in diabetes is a potential regulator of mesangial cell-matrix interactions through transmembrane matrix receptors. We now provide evidence that PG production from rat glomerular mesangial cells is increased by Fn. An increase in PG (measured as PGE) was demonstrated in mesangial cell-enriched glomerular cores after 1-h exposure (149 +/- 8% of timed control) and was sustained over a 24-h period (214 +/- 7%). Increased PG production followed exposure to a chymotryptic fragment (120,000 M(r)) of Fn and occurred concomitant with an increase in particulate PKC activity. A tetrapeptide (Arg-Gly-Asp-Ser) with the Arg-Gly-Asp sequence, contained in Fn and the chymotryptic fragment and recognized by specific membrane receptors (integrin matrix-binding proteins), also raised PG levels. As has been shown previously, exposure to high glucose concentration can increase mesangial cell PGE production (from 677 +/- 61 pg.mg protein-1.2 h-1 at 5.6 mM glucose to 1561 +/- 132 pg.mg protein-1.2 h-1 at 50 mM glucose, P < 0.001). The response to the chymotryptic fragment of Fn also was enhanced by concurrent exposure to high glucose concentration (from 2560 +/- 199 pg.mg protein-1.2 h-1 at 5.6 mM glucose to 4672 +/- 358 pg.mg protein-1.2 h at 50 mM glucose, P < 0.001). Coincubation with H-7, an inhibitor of PKC, abolished the PG response to glucose and the chymotryptic fragment. Involvement of PKC was supported further by abrogation of the effect of chymotryptic fragment in mesangial cells cultured for a prior prolonged period with phorbol ester.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of cyclic AMP levels by calcium in bovine adrenal medullary cells

Both nicotine and histamine have been reported to increase cyclic AMP levels in chromaffin cells by Ca(2+)-dependent mechanisms. The present study investigated whether Ca2+ was an adequate and sufficient signal for increasing cyclic AMP in cultured bovine adrenal medullary cells. Depolarization with 50 mM K+ caused a two- to three-fold increase in cellular cyclic AMP levels over 5 min, with no change in extracellular cyclic AMP. This response was abolished by omission of extracellular Ca2+ and by 100 microM methoxyverapamil, and was unaffected by 1 microM tetrodotoxin and by 1 mM isobutylmethylxanthine. Veratridine (40 microM) also increased cellular cyclic AMP levels by two- to fourfold. This response was abolished by either methoxyverapamil or tetrodotoxin. The Ca2+ ionophore A23187 (10-50 microM) had little or no effect on cellular cyclic AMP levels. When the concentration of K+ used to depolarize the cells was reduced to 12-15 mM, the catecholamine release was similar to that induced by 50 microM A23187, and the cyclic AMP response was almost abolished. The results suggest that Ca2+ entry into chromaffin cells is a sufficient stimulus for increasing cellular cyclic AMP production. The possible involvement of a Ca2+/calmodulin-dependent isozyme of adenylate cyclase is discussed.