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In Nyāya philosophy, a special kind of extraordinary sensory connection is admitted named jñānalakṣaṇā pratyāsatti or jñānalakṣaṇa sannikarṣa. It is held that sometimes our sense-organ can be connected to such an object which is not amenable to the operating sense-organ. In such cases, cognition (jñāna) plays the role of sensory connection and connects the content of itself to the operating sense-organ. The paradigmatic example of jñānalakṣaṇa perception is to ‘see’ fragrant sandal through visual sense from non-smellable distance. This hypothesis of (...) jñānalakṣaṇa has been criticized by the opponents being considered as counterintuitive, mysterious and theoretically overloaded. This paper tries to demystify the notion. It shows that although it seems to be metaphysically mysterious phenomenon at first sight, it is not so at all. The paper explores the psychological process involved in this sensory connection. The hypothesis is shown to have sufficient explanatory power, because the Naiyāyikas have used this hypothesis to explain five different epistemic situations. Hence, this paper argues that it is not a theoretical overload. The opponents counter-argue that all those five cognitive situations can be explained without admitting jñānalakṣaṇa. Moreover, if we admit jñānalakṣaṇa, then a particular kind of inference will become redundant. The paper answers all those objections and defends the hypothesis. The second part of the paper presents an empirical evidence in support of the hypothesis. The arguments leveled against the hypothesis of jñānalakṣaṇa can be contested on the ground that they try to disprove something which is supported on experimental ground. Experiments represent universally acceptable objective facts supported by experience—denying which amounts to anubhavavirodha, which philosophers would want to avoid. Hence, supporting jñānalakṣaṇa on the ground of scientific experiments can be considered as a philosophical stand. Now, there is a clinically recognized and neurophysiologically proved condition, called synaesthesia, where stimulation of a particular sensory modality automatically and involuntarily activates a different sensory modality simultaneously without a direct stimulation of the second modality. As for example, when a sound → colour synaesthete listens to a particular tone such as C-sharp, she visualizes particular colour, such as blue, in her mind’s eye; for a grapheme → colour synaesthete a particular number or alphabet is always tinged with a particular colour. This paper shows that the cognitive process involved in synaesthesia lends support to the hypothesis of jñānalakṣaṇa pratyāsatti. It has been proved through several experiments that it is a genuine perceptual phenomenon and is not a confabulation of memory. There are several alternative theories which explain the phenomenon neurophysiologically. The paper discusses the most popular one: the cross-activation hypothesis. There are two major objections against the project of comparing jñānalakṣaṇa with synaesthesia. First, synaesthesia is a neurological condition present in a few numbers of people whereas jñānalakṣaṇa is claimed to be universal phenomenon. Second, syneasthesia is a sensory experience whereas jñānalakṣaṇa involves application of concepts. The paper answers these questions. Firstly, multimodal processing in the brain is a universal phenomenon; secondly, there is a form of synaesthesia where top-down processing is involved. In those cases, concepts play important role for having synaesthetic experience. (shrink)

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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 GABAergic 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. On this proposal, binding processes that do not normally generate awareness become accessible to consciousness as a result of decreased attentional discrimination among incoming stimuli. (shrink)

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Synaesthesia is a condition in which one type of stimulation evokes the sensation of another, as when the hearing of a sound produces photisms, i.e. mental percepts of colours. R is a 20 year old colour blind subject who, in addition to the relatively common grapheme-colour synaesthesia, presents a rarely reported cross modal perception in which a variety of visual stimuli elicit aura-like percepts of colour. In R, photisms seem to be closely related to the affective valence of stimuli and (...) typically bring out a consistent pattern of emotional responses. The present case study suggests that colours might be an intrinsic category of the human brain. We developed an empirical methodology that allowed us to study the subject's otherwise inaccessible phenomenological experience. First, we found that R shows a Stroop effect elicited by photisms despite the fact that he does not show a regular Stroop with real colours. Secondly, by manipulating the colour context we confirmed that colours can alter R's emotional evaluation of the stimuli. Furthermore, we demonstrated that R's auras may actually lead to a partially inverted emotional spectrum where certain stimuli bring out emotional reactions opposite to the normal ones. These findings can only be accounted for by considering R's subjective colour experience or qualia. Therefore the present paper defends the view that qualia are a useful scientific concept that can be approached and studied by experimental methods. (shrink)

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We propose that there are four fundamental kinds of metaphor that are uniquely mapped onto specific brain ‘‘networks’’ and present preliterate (i.e., evolutionary, including before the appearance of written language in the historical record), prelinguistic (i.e., developmental, before the appearance of speech in human development), and extralinguistic (i.e., neuropsychological, cognitive) evidence supportive of this view. We contend that these basic metaphors are largely nonconceptual and entail (a) perceptual–perceptual, (b) cross-modal, (c) movement–movement, and (d) perceptual-affective mappings that, at least, in the (...) initial stages of processing may operate largely outside of conscious awareness. In opposition to our basic metaphor theory (BmT), the standard theory (SmT) maintains that metaphor is a conceptual mapping from some base domain to some target domain and/or represents class-inclusion (categorical) assertions. The SmT captures aspects of secondary or conceptual metaphoric relations but not primary or basic metaphoric relations in our view. We believe our theory (BmT) explains more about how people actually recognize or create metaphoric associations across disparate domains of experience partly because they are ‘‘pre-wired’’ to make these links. (shrink)

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