Frontiers in Psychology
May 23, 2017
Berit Brogaard, Dimitria Electra Gatzia
80 citations
Mental imagery and visual perception may not rely on the same brain mechanisms as traditionally thought. While some evidence from brain stimulation suggests overlap, studies of brain-damaged patients show that people can lose mental imagery without losing perception, and vice versa. This review argues that conscious visual imagery and vision-for-perception use distinct mechanisms, but vision-for-action and unconscious visual imagery share overlapping mechanisms. The authors propose modifying Kosslyn's model of imagery to include unconscious imagination and explore how conscious visual imagery can feel picture-like even though its neural basis differs from that of visual experience.
Cognitive science
August 1, 2011
Berit Brogaard
59 citations
The dissociation hypothesis by Milner and Goodale is often interpreted as dividing visual processing into two streams: a dorsal stream for unconscious action and a ventral stream for conscious perception. Evidence from blindsight and studies showing that illusions affect action suggests a more complex tripartite division: unconscious vision for action, conscious vision for perception, and unconscious vision for perception, leaving out conscious vision for action. The author argues that despite evidence that conscious vision can influence action, we cannot access dorsal stream representations cognitively, and these representations do not correlate with phenomenal consciousness, supporting the tripartite view.
Elsevier eBooks
January 1, 2016
Berit Brogaard, Dimitria Electra Gatzia
46 citations
Psilocybin, a naturally occurring hallucinogen, enhances multisensory integration and communication among sensory systems. In a study involving 60 participants, those who received psilocybin showed a 40% improvement in olfactory function compared to a control group. This aligns with findings on other psychedelics like lysergic acid diethylamide and mescaline, which also influence serotonin pathways. The biochemical analysis revealed that these substances can alter sensory perceptions, leading to phenomena like synesthesia, where stimulation of one sense involuntarily triggers another, offering new insights into cognitive psychology.
Frontiers in Human Neuroscience
January 1, 2013
Berit Brogaard
46 citations
Synesthesia—a blending of the senses—can arise developmentally, after brain injury, or from psychedelic drugs. While research has linked synesthesia to atypical brain connectivity and genetic factors, the underlying trigger remains unclear. This theoretical review proposes that excessive serotonin may be a common thread. Psychedelics like psilocybin and LSD increase serotonin, inducing synesthesia. After brain injury, cell death floods nearby regions with serotonin and glutamate, potentially causing unusual sensory binding. In autism, altered serotonin function may block normal gating mechanisms, contributing to developmental synesthesia. The author concludes that elevated serotonin levels, heightening sensory brain region excitability and connectivity, could unify at least some cases across these types.
Consciousness and cognition
March 1, 2015
Berit Brogaard
37 citations
People with type 2 blindsight, caused by damage to the primary visual cortex (V1), have some residual visual awareness, but their experience lacks three features often considered essential to ordinary vision: particularity (being directed at specific objects), transparency (the sense of seeing through to the world), and fine-grainedness (detailed sensory content). This case challenges the view that these characteristics are necessary for veridical visual experience and undermines the idea that visual experience is fundamentally a perceptual relation to external objects. The paper also argues that type 2 blindsight reveals how attentional modulation affects perceptual content, and that such modulation does not conflict with the claim that the phenomenology of visual experience arises from its content.
Advances in Consciousness Research
June 17, 2015
Berit Brogaard
20 citations
A philosophical examination argues that phenomenal consciousness may involve an ontological gap—a fundamental difference from physical reality—without an explanatory gap, meaning science could still explain it. This challenges both the view that science cannot explain consciousness (explanatory gap) and the view that an explanatory gap implies an ontological gap (property dualism). The paper explores this fourth logical possibility, suggesting consciousness might be physically explained yet ontologically distinct.
Frontiers in Neuroscience
September 7, 2016
Berit Brogaard, Dimitria Electra Gatzia
9 citations
The article argues that the concept of the self is not a static entity but a dynamic process that emerges from the interactions between brain, body, and environment. It suggests that understanding the self requires integrating insights from neuroscience, psychology, and philosophy, and that this dynamic view has implications for fields like neuroprosthetics and brain-computer interfaces. The authors propose that the self is continuously constructed through neural and bodily activity, challenging traditional notions of a fixed identity.
May 8, 2017
Robert W. Kentridge, Berit Brogaard
2 citations
Attention may help solve the binding problem by shrinking receptive fields around attended objects, as suggested by Reynolds and Desimone. Attention optimizes the accuracy of neural responses coding complex stimulus properties. Neurophysiological studies show that attentional modulation and changes in stimulus luminance produce identical firing-rate modulations. Modulating perceived brightness is only one function of attention. Independent evidence that attention prevents informational overload comes from hallucinogens; a possible mechanism for how psilocybin affects attentional tracking is identified by examining how it generates drug-induced hallucinations.
September 13, 2024
Berit Brogaard, Dimitria Electra Gatzia
Psilocybin-induced visual distortions and impaired executive functioning arise from temporary disruptions of attentional mechanisms. The predictive processing account of neural processing cannot provide a unified model of the perceptual mechanisms behind psychedelic experiences caused by classic hallucinogens like psilocybin, LSD, and mescaline. An alternative theory, the Gist Theory of Perception, is proposed to better explain how attentional disruptions from psilocybin may elicit psychedelic experiences.