Berit Brogaard

Type 2 blindsight and the nature of visual experience

Blindsight is a kind of residual vision found in people with lesions to V1. Subjects with blindsight typically report no visual awareness, but they are nonetheless able to make above-chance guesses about the shape, location, color and movement of visual stimuli presented to them in their blind field. A different kind of blindsight, sometimes called type 2 blindsight, is a kind of residual vision found in patients with V1 lesions in the presence of some residual awareness. Type 2 blindsight differs from ordinary visual experience in lacking the particularity, transparency and fine-grainedness often taken to be essential to visual experience, at least in veridical cases. I argue that the case of type 2 blindsight provides a counterexample to the view that these characteristics are essential to veridical visual experience and that this gives us reason to resist the view that visual experience is essentially a perceptual relation to external objects. In the second part of the paper I argue that the case of type 2 blindsight yields important insights into the effects of attentional modulation on perceptual content and that cases of attentional modulation of appearance are not at odds with the view that the phenomenology of visual experience flows from its content.

Is Color Experience Cognitively Penetrable

Is color experience cognitively penetrable? Some philosophers have recently argued that it is. In this paper, we take issue with the claim that color experience is cognitively penetrable. We argue that the notion of cognitive penetration that has recently dominated the literature is flawed since it fails to distinguish between the modulation of perceptual content by non-perceptual principles and genuine cognitive penetration. We use this distinction to show that studies suggesting that color experience can be modulated by factors of the cognitive system do not establish that color experience is cognitively penetrable. Additionally, we argue that even if color experience turns out to be modulated by color-related beliefs and knowledge beyond non-perceptual principles, it does not follow that color experience is cognitively penetrable since the experiences of determinate hues involve post-perceptual processes. We conclude with a brief discussion of the implications that these ideas may have on debates in philosophy.

What Can Neuroscience Tell Us about the Hard Problem of Consciousness

A main research goal within neuroscience is to explain the relation between neurophysiological processes and conscious experiences. One approach involves focusing on problems such as the integration of information, the deliberate control of behavior, the ability to discriminate and categorize environmental stimuli, etc. These problems have been dubbed by philosophers as “easy” to suggest that the present limitations hindering progress could be overcome by more sophisticated methods in the near future (Chalmers, 1995, 1996). For example, explaining the integration of information requires describing the neurophysiological mechanisms responsible for information processing. Although these mechanisms are not currently well known, it is very likely that neuroscience will be able to explain them in the near future. It has been argued, however, that the problem of phenomenal consciousness cannot be explained by reference to such mechanisms because it involves a special kind of subjective qualities, i.e., phenomenal qualities that are present in experience (Dennett, 1991, 2003; Block, 1995; Chalmers, 1996; Revonsuo, 2006; Majeed, 2016). For example, the experience of seeing a red patch has a different phenomenal quality (a redly quality or “feel”) from the experience of seeing a green patch (a greenly quality or “feel”)1. The problem of explaining how or why neurophysiological processing gives rise to phenomenal experiences has been dubbed the “hard problem of consciousness” to suggest that solving it requires a paradigm shift in neuroscience (Chalmers, 1995, 1996).

The Self-Locating Property Theory of Color

The paper reviews the empirical evidence for highly significant variation across perceivers in hue perception and argues that color physicalism cannot accommodate this variability. Two views that can accommodate the individual differences in hue perception are considered: the self-locating property theory, according to which colors are self-locating properties, and color relationalism, according to which colors are relations to perceivers and viewing conditions. It is subsequently argued that on a plausible rendition of the two views, the self-locating theory has a slight advantage over color relationalism in being truer to the phenomenology of our color experiences.

Unconscious Imagination and the Mental Imagery Debate

Traditionally, philosophers have appealed to the phenomenological similarity between visual experience and visual imagery to support the hypothesis that there is significant overlap between the perceptual and imaginative domains. The current evidence, however, is inconclusive: while evidence from transcranial brain stimulation seems to support this conclusion, neurophysiological evidence from brain lesion studies (e.g., from patients with brain lesions resulting in a loss of mental imagery but not a corresponding loss of perception and vice versa) indicates that there are functional and anatomical dissociations between mental imagery and perception. Assuming that the mental imagery and perception do not overlap, at least, to the extent traditionally assumed, then the question arises as to what exactly mental imagery is and whether it parallels perception by proceeding via several functionally distinct mechanisms. In this review, we argue that even though there may not be a shared mechanism underlying vision for perception and conscious imagery, there is an overlap between the mechanisms underlying vision for action and unconscious visual imagery. On the basis of these findings, we propose a modification of Kosslyn’s model of imagery that accommodates unconscious imagination and explore possible explanations of the quasi-pictorial phenomenology of conscious visual imagery in light of the fact that its underlying neural substrates and mechanisms typically are distinct from those of visual experience.

Pre-cueing, Perceptual Learning and Cognitive Penetration

In The Principles of Psychology, James (1981) suggested that attending to a stimulus can make it appear more “vivid and clear.” Pre-cueing, the procedure in which a cue stimulus is presented to direct a subject’s attention to the location of a test stimulus, has been used to test James’ hypothesis (Posner, 1978, 1980; Carrasco et al., 2004, 2006; Yeshurun and Rashal, 2010; Carrasco, 2011; Kravitz and Behrmann, 2011). A recent debate concerns whether pre-cueing effects associated with covert attention involve cognitive penetration. In the context of information processing, cognitive penetration occurs when the information content of cognitive states directly influences perceptual computations in such a way as to alter their output1. Attention is the process that either enhances the representation of relevant information (e.g., a scene at a certain location or an aspect of a visual scene) at the system level or diminishes the representation of irrelevant noise. Studies show that attention boosts the apparent stimulus contrast (Carrasco et al., 2004) and increases contrast sensitivity, which seems to be mediated by contrast grain—an effect akin to a change in the physical contrast stimulus (Carrasco et al., 2006). In addition, attention enhances spatial identification accuracy (Yeshurun and Rashal, 2010) and aids in the segmentation of the retinal image by increasing both firstand second-order sensitivity to the attended location (Barbot et al., 2012). Attention can be allocated either by some bodily orientation of the organs by which an organism moves, say, when the eyes move in the direction of a target location (overt attention) or by shifting the direction of attention without reorienting the body, say, when attention is drawn by the salience of a cue while the eyes remain fixed (covert attention, see Findlay and Gilchrist, 2003). Cases that involve overt attention are not treated as cases of cognitive penetration because overt attention functions as a passive partition mechanism acting prior to the beginning of perceptual process (Pylyshyn, 1999; Macpherson, 2012; Deroy, 2013; Mole, 2015; Firestone and Scholl, 2016; Brogaard and Gatzia, 2017). Recently, however, it has been suggested that cases of covert attention are instances of cognitive penetration (Mole, 2015; Wu, in press) because covert attention functions as an active controlling influence of perceptual processing (Nanay, 2010; Carrasco, 2011, 2014). Overt and covert attention can be exogenous or endogenous. Exogenous attention corresponds to a reflexive, involuntary response to a location upon the occurrence of a sudden or intense stimulation—it is oriented in a stimulus-driven or bottom-up manner (Carrasco, 2006, 2011). For example, when letters appear abruptly on a computer screen, they capture the eyes’ attention and elicit faster responses than when they appear gradually (Yantis and Jonides, 1984; Jonides and Yantis, 1988). Endogenous attention corresponds to our ability to monitor stimulus information (typically based on a cue) voluntarily—it is oriented in a goal-driven or top-down manner (Carrasco, 2006, 2011). For example, we often prepare for an expected event by orienting attention

Psilocybin, Lysergic Acid Diethylamide, Mescaline, and Drug-Induced Synesthesia

Studies have shown that both serotonin and glutamate receptor systems play a crucial role in the mechanisms underlying drug-induced synesthesia. The specific nature of these mechanisms, however, continues to remain elusive. Here we propose two distinct hypotheses for how synesthesia triggered by hallucinogens in the serotonin agonist family may occur. One hypothesis is that the drug-induced destabilization of thalamic projections via γ-aminobutyric acidergic neuronal circuits from sensory areas leads to a disruption of low-level, spontaneous integration of multisensory stimuli. This sort of integration regularly occurs when spatial and temporal attributes match. Destabilization of feedback loops, however, can result in incongruent experiences or binding of random thalamus activation with sensory input in a particular sensory modality. The second hypothesis builds on embodied cognition, cases in which visual images of external stimuli activate task-related neural regions. In this proposal, binding processes that do not normally generate awareness become accessible to consciousness as a result of decreased attentional discrimination among incoming stimuli.

Is the Auditory System Cognitively Penetrable

According to the hierarchical model of sensory information processing, sensory inputs are transmitted to cortical areas, which are crucial for complex auditory and speech processing, only after being processed in subcortical areas (Hickok and Poeppel, 2007; Rauschecker and Scott, 2009). However, studies using electroencephalography (EEG) indicate that distinguishing simultaneous auditory inputs involves a widely distributed neural network, including the medial temporal lobe, which is essential for declarative memory, and posterior association cortices (Alain et al., 2001; Squire et al., 2004). More recent studies have even demonstrated plasticity of auditory signals as low as the brainstem (Suga, 2008). Collectively, studies suggest that the functional architecture of perceptual processing involves primarily top-down modulation (Suga et al., 2002; Gilbert and Li, 2013; Chandrasekaran et al., 2014). Top-down influences exerted throughout the auditory systems (Lotto and Holt, 2011) include: memory (Goldinger, 1998)1, attention (Choi et al., 2014), which has been found to modulate auditory encoding in the cochlea, a subcortical area (Maison et al., 2001), (prior) knowledge of syntax or words (Ganong, 1980; Warren, 1984)2, and experience-based expectations pertaining to the speakers accent (Deutsch, 1996; Deutsch et al., 2004; Irino and Patterson, 2006), gender (Johnson et al., 1999), and vocal folds or tract (Irino and Patterson, 2002; Patterson and Johnsrude, 2008).

In defense of hearing meanings

According to the inferential view of language comprehension, we hear a speaker’s utterance and infer what was said, drawing on our competence in the syntax and semantics of the language together with background information. On the alternative perceptual view, fluent speakers have a non-inferential capacity to perceive the content of speech. On this view, when we hear a speaker’s utterance, the experience confers some degree of justification on our beliefs about what was said in the absence of defeaters. So, in the absence of defeaters, we can come to know what was said merely on the basis of hearing the utterance. Several arguments have been offered against a pure perceptual view of language comprehension, among others, arguments pointing to its alleged difficulties accounting for homophones and the context-sensitivity of ordinary language. After responding to challenges to the perceptual view of language comprehension, I provide a new argument in favor of the perceptual view by looking closer at the dependence of the justificatory qualities of experience on the notion of a defeater as well as the perceptual nature of language learning and language processing.

Deaf hearing: Implicit discrimination of auditory content in a patient with mixed hearing loss

Abstract We describe a patient LS, profoundly deaf in both ears from birth, with underdeveloped superior temporal gyri. Without hearing aids, LS displays no ability to detect sounds below a fixed threshold of 60 dBs, which classifies him as clinically deaf. Under these no-hearing-aid conditions, when presented with a forced-choice paradigm in which he is asked to consciously respond, he is unable to make above-chance judgments about the presence or location of sounds. However, he is able to make above-chance judgments about the content of sounds presented to him under forced-choice conditions. We demonstrated that LS has faint sensations from auditory stimuli, but questionable awareness of auditory content. LS thus has a form of type-2 deaf hearing with respect to auditory content. As in the case of a subject with acquired deafness and deaf hearing reported on a previous occasion, LS’s condition of deaf hearing is akin in some respects to type-2 blindsight. As for the case of type 2 blindsight the case indicates that a form of conscious hearing can arise in the absence of a fully developed auditory cortex.