Investigating neural, behavioural and subjective correlates of individual differences in mental imagery

EMBARGOED - expected end date 26.05.202

Mental imagery and visual attentional templates: a dissociation

There is a growing interest in the relationship between mental images and attentional templates as both are considered pictorial representations that involve similar neural mechanisms. Here, we investigated the role of mental imagery in the automatic implementation of attentional templates and their effect on involuntary attention. We developed a novel version of the contingent capture paradigm designed to encourage the generation of a new template on each trial and measure contingent spatial capture by a template-matching visual feature (color). Participants were required to search at four different locations for a specific object indicated at the start of each trial. Immediately prior to the search display, color cues were presented surrounding the potential target locations, one of which matched the target color (e.g., red for strawberry). Across three experiments, our task induced a robust contingent capture effect, reflected by faster responses when the target appeared in the location previously occupied by the targetmatching cue. Contrary to our predictions, this effect remained consistent regardless of self-reported individual differences in visual mental imagery (Experiment 1, N = 216) or trial-by-trial variation of voluntary imagery vividness (Experiment 2, N = 121). Moreover, contingent capture was observed even among aphantasic participants, who report no imagery (Experiment 3, N = 91). The magnitude of the effect was not reduced in aphantasics compared to a control sample of non-aphantasics, although the two groups reported substantial differences in their search strategy and exhibited differences in overall speed and accuracy. Our results hence establish a dissociation between the generation and implementation of attentional templates for a visual feature (color) and subjectively experienced imagery.</p

Inflammation-induced reorientation of reward versus punishment sensitivity is attenuated by Minocycline

Inflammation rapidly reorients motivational state, mood is impaired, pleasurable activities avoided and sensitivity to negative stimuli enhanced. When sustained, this can precipitate major depressive episodes. In humans, this has been linked to opposing actions of inflammation on striatal/insula reward/punishment learning signals while in rodents, motivational impairments can be attenuated with minocycline, implicating a mechanistic role for microglia. Here we investigated whether minocycline also inhibits the reorienting effects of lipopolysaccharide (LPS) on reward/punishment sensitivity in humans. Methods Using a crossover design, fifteen healthy volunteers underwent two experimental sessions in which they each received LPS (1ng/kg) and placebo. Half (N=8) received minocycline (100 mg bd) and half (N=7) an identical looking placebo for 3½ days before each session. Six hours post-injection participants completed a probabilistic instrumental learning task in which they had to learn to select high probability reward (win £1) and avoid high probability punishment (lose £1) stimuli to maximise their gains and minimize losses. Physiological and sickness responses were sampled hourly and blood sampled at baseline, 3 and 6 hours post-injection. Results LPS induced robust peripheral physiological: temperature, heart rate and immune: differential white cell, IL-6, TNF-α, IL-8, IL-10 responses (all condition x time interactions: p0.1). LPS also biased behavior, enhancing punishment compared with reward sensitivity (F(1,13)=6.10, p=0.028). Minocycline significantly attenuated this inflammation-induced shift in reward versus punishment sensitivity (F(1,13)=4.28, p=0.033). Conclusions These data replicate the previous finding that systemic inflammation rapidly impairs sensitivity to rewards versus punishments in humans and extend this by implicating activated microglia in this acute motivational reorientation with implications for the development of microglial-targeted immune-modulatory therapies in depression

Mental imagery and visual attentional templates: a dissociation

There is a growing interest in the relationship between mental images and attentional templates as both are considered pictorial representations that involve similar neural mechanisms. Here, we investigated the role of mental imagery in the automatic implementation of attentional templates and their effect on involuntary attention. We developed a novel version of the contingent capture paradigm designed to encourage the generation of a new template on each trial and measure contingent spatial capture by a template-matching visual feature (color). Participants were required to search at four different locations for a specific object indicated at the start of each trial. Immediately prior to the search display, color cues were presented surrounding the potential target locations, one of which matched the target color (e.g., red for strawberry). Across three experiments, our task induced a robust contingent capture effect, reflected by faster responses when the target appeared in the location previously occupied by the targetmatching cue. Contrary to our predictions, this effect remained consistent regardless of self-reported individual differences in visual mental imagery (Experiment 1, N = 216) or trial-by-trial variation of voluntary imagery vividness (Experiment 2, N = 121). Moreover, contingent capture was observed even among aphantasic participants, who report no imagery (Experiment 3, N = 91). The magnitude of the effect was not reduced in aphantasics compared to a control sample of non-aphantasics, although the two groups reported substantial differences in their search strategy and exhibited differences in overall speed and accuracy. Our results hence establish a dissociation between the generation and implementation of attentional templates for a visual feature (color) and subjectively experienced imagery.</p

Investigating relationships between trait visual imagery and phenomenological control: the role of context effects

Phenomenological control is the ability to alter experience according to goals, measured by responses to imaginative suggestion. The capacity to create vivid mental imagery has been thought to contribute to generation of experiences following suggestions during hypnosis, but evidence is mixed. Moreover, no study has yet investigated this link outside of hypnosis. Across two studies (n = 639 and n = 66), we tested the relationship between imagery vividness and both non-hypnotic and hypnotic imaginative suggestion scales. Our samples included, for the first time, people lacking voluntary imagery (aphantasics). We also assessed this relationship following commonly used approaches to studying aphantasia (direct recruitment of self-reported aphantasics), versus those designed to minimize demand characteristics effects. We observed a weak positive relationship between imagery vividness and phenomenological control, with aphantasics being slightly lower in this trait than non-aphantasics. However, this effect was exaggerated among self-reported aphantasics, who scored lower on phenomenological control than samples experiencing imagery as well as aphantasics assessed via single-blind procedure. Our results have been certified as computationally reproducible by an independent statistician. We conclude that, while imagery may contribute to responding to imaginative suggestions, it is crucial to follow single-blind recruitment to reduce the effect of demand characteristics.</p

Inflammation-induced reorientation of reward versus punishment sensitivity is attenuated by Minocycline

Inflammation rapidly reorients motivational state, mood is impaired, pleasurable activities avoided and sensitivity to negative stimuli enhanced. When sustained, this can precipitate major depressive episodes. In humans, this has been linked to opposing actions of inflammation on striatal/insula reward/punishment learning signals while in rodents, motivational impairments can be attenuated with minocycline, implicating a mechanistic role for microglia. Here we investigated whether minocycline also inhibits the reorienting effects of lipopolysaccharide (LPS) on reward/punishment sensitivity in humans. Methods Using a crossover design, fifteen healthy volunteers underwent two experimental sessions in which they each received LPS (1ng/kg) and placebo. Half (N=8) received minocycline (100 mg bd) and half (N=7) an identical looking placebo for 3½ days before each session. Six hours post-injection participants completed a probabilistic instrumental learning task in which they had to learn to select high probability reward (win £1) and avoid high probability punishment (lose £1) stimuli to maximise their gains and minimize losses. Physiological and sickness responses were sampled hourly and blood sampled at baseline, 3 and 6 hours post-injection. Results LPS induced robust peripheral physiological: temperature, heart rate and immune: differential white cell, IL-6, TNF-a, IL-8, IL-10 responses (all condition x time interactions: p0.1). LPS also biased behavior, enhancing punishment compared with reward sensitivity (F(1,13)=6.10, p=0.028). Minocycline significantly attenuated this inflammation-induced shift in reward versus punishment sensitivity (F(1,13)=4.28, p=0.033). Conclusions These data replicate the previous finding that systemic inflammation rapidly impairs sensitivity to rewards versus punishments in humans and extend this by implicating activated microglia in this acute motivational reorientation with implications for the development of microglial-targeted immune-modulatory therapies in depression