Right Broca’s area is hyperactive in right-handed subjects during meditation: Possible clinical implications?
Introduction
Broca’s areas, conventionally located in the left hemisphere, not only participate in its primary function-expressive language processing but in secondary functions-processing non-linguistic/nonverbal tasks as well [1], [2]. Paul Broca first identified this area on the left side, and correlated this to speech and language tasks [3]. Since then, large number of studies have affirmed its location in left hemisphere [4], and its functionality in processing the integrated linguistic and non-linguistic tasks. The presence of left Broca’s area in the categorical i.e., left hemisphere is based on the fact that in 96% of right-handed individuals, who constitute 91% of human population, the left hemisphere is the dominant or categorical hemisphere, and in 70% of left-handers also the left hemisphere is the categorical hemisphere [5]. In-line with these findings, it has been shown that in almost all right-handed persons and majority of left-handed persons, the language skills such as naming [6], phonology [7], [8], semantics [9], [10], [11] and syntax [12], [13], [14] are concentrated in the left hemisphere. Furthermore, in great apes it was shown that the inferior frontal region corresponding to human Broca’s region is larger in the left than in the right hemisphere, which suggests left-hemisphere dominance in vocalization emerged as early as five million years ago, long before speech emerged [15]. Nonetheless, it has been shown that the homolog of Broca’s area in right brain (referred to as right Broca’s area) is also involved in language and speech tasks, particularly communicative and emotional prosody and pragmatics of language [16], [17] intonation and orchestrating speech articulation [18], [19], [20]. The evidence for this comes from the finding that patients with right anterior lesions showed altered intonation [21]. It has also been suggested that though adults may have limited plasticity of brain, i.e., they suffer a permanent damage to language and speech tasks if left brain is removed, but infants learn to speak fluently even if the left brain is removed [22], [23]. This indicates that it is the training that activates and increases functionality of right brain, possibly engaging the corresponding right Broca’s area with unknown but important functionality. Herein, we introduce novel scientific-based hypothesis of hyperactivity of right homolog of Broca’s region during meditation and its possible role to explore in patients with language and attention disorders.
Section snippets
The hypothesis
Based on our recent observations [24] that long-term and regular practice of meditation activate specific brain regions of right hemisphere associated with focused attention task i.e., meditation evaluated by innovative 18FDG-PET methodological approach, we further hypothesize that it may play an important role in clinical conditions like attention deficient syndrome, language and speech disorders.
Evaluation of the hypothesis
Literatures were extensively searched to formulate our suggested hypothesis based on the novel findings of the functionality of right homolog of Broca area. Retrospective data from patients with Broca’s aphasia shows that it is basically the left Broca’s area that is implicated in compromised speech and language tasks, which supported the data from previous studies where lesions were identified in left Broca’s area. Research using repetitive transcranial magnetic stimulation (rTMS) in brain
Investigational observation
The specific areas in brain which were hyperactive during meditation using 18FDG-PET have been published previously [24]. Meditation includes self-regulation practices that focus on training attention and awareness to achieve better control on mental processes [31]. There are various ways of doing meditation but basic features common to all types of meditation are sensory attenuation, minimum efferent output, and targeted non-analytical thinking. Most of the previous studies used fMRI and only
Consequences of hypothesis
Present hypothesis may ignite new research towards studies based on present hypothesis points that include:
- a)
Meditation, a non-pharmacological therapy may provide the clinical and empirical support to the patients with language and speech disorders.
- b)
Long-term and regular practice of meditation may help in improving focused-attention related tasks, further may be beneficial for ADHD patients.
Conclusion
Our recent study findings suggest that right Broca’s area may play an important role in attention, speech and language related tasks, and mediation may be a promising alternative therapy in ADHD. The meditation can activate the right Broca’s area, which further can be explored clinically for attention, speech and language therapy in patients who have lesions in their left Broca’s area.
Author contributions
Dipti Magan: Implemented the idea for this review, literatures search, and drafted initial manuscript; Raj Kumar Yadav: Contributed towards review concept and helped in revising the manuscript.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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