Subjective Somatosensory Experiences Disclosed by Focused Attention: Cortical-Hippocampal-Insular and Amygdala Contributions Clemens C. C. Bauer 1 , Fernando A. Barrios 1 *, Jose ´-Luis Dı´az 2 * 1 Laboratorio de Neuroimagen Functional, Instituto de Neurobiologı ´a, Universidad Nacional Auto ´noma de Me ´xico, Quere ´taro, Me ´xico, 2 Departamento de Historia y Filosofı ´a de la Medicina, Facultad de Medicina, Universidad Nacional Auto ´ noma de Me ´xico, Me ´xico, D. F., Me ´xico Abstract In order to explore the neurobiological foundations of qualitative subjective experiences, the present study was designed to correlate objective third-person brain fMRI measures with subjective first-person identification and scaling of local, subtle, and specific somatosensory sensations, obtained directly after the imaging procedure. Thus, thirty-four volunteers were instructed to focus and sustain their attention to either provoked or spontaneous sensations of each thumb during the fMRI procedure. By means of a Likert scale applied immediately afterwards, the participants recalled and evaluated the intensity of their attention and identified specific somatosensory sensations (e.g. pulsation, vibration, heat). Using the subject’s subjective scores as covariates to model both attention intensity and general somatosensory experiences regressors, the whole-brain random effect analyses revealed activations in the frontopolar prefrontal cortex (BA10), primary somatosensory cortex (BA1), premotor cortex (BA 6), precuneus (BA 7), temporopolar cortex (BA 38), inferior parietal lobe (BA 39), hippocampus, insula and amygdala. Furthermore, BA10 showed differential activity, with ventral BA10 correlating exclusively with attention (r(32) = 0.54, p = 0.0013) and dorsal BA10 correlating exclusively with somatosensory sensation (r(32) = 0.46, p = 0.007). All other reported brain areas showed significant positive correlations solely with subjective somatosensory experiences reports. These results provide evidence that the frontopolar prefrontal cortex has dissociable functions depending on specific cognitive demands; i.e. the dorsal portion of the frontopolar prefrontal cortex in conjunction with primary somatosensory cortex, temporopolar cortex, inferior parietal lobe, hippocampus, insula and amygdala are involved in the processing of spontaneous general subjective somatosensory experiences disclosed by focused and sustained attention. Citation: Bauer CCC, Barrios FA, Dı ´az J-L (2014) Subjective Somatosensory Experiences Disclosed by Focused Attention: Cortical-Hippocampal-Insular and Amygdala Contributions. PLoS ONE 9(8): e104721. doi:10.1371/journal.pone.0104721 Editor: Krish Sathian, Emory University, United States of America Received March 19, 2014; Accepted July 15, 2014; Published August 28, 2014 Copyright: ß 2014 Bauer et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that, for approved reasons, some access restrictions apply to the data underlying the findings. Data are available from the Qualia Study, corresponding author FAB may be contacted at fbarrios@unam.mx to gain access to our institutional data server. Funding: C. C. C. B. is a doctoral student from ‘‘Programa de Doctorado en Ciencias Biome ´ dicas’’, Universidad Nacional Auto ´ noma de Me ´xico (UNAM) and received the doctoral scholarship 250718 from The Consejo Nacional de Ciencia y Tecnologı ´a, Mexico, the National Council of Science and Technology (CONACyT). This project was partially funded by CONACyT CB167271. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * Email: barrios@inb.unam.mx (FAB); jldiaz43@gmail.com (JLD) Introduction Before attempting to explain how and why neurophysiological processes relate to consciousness traits, it seems necessary to find consistent correlations between subjective phenomenological features and brain activity patterns [1]. For example, it is now possible to correlate introspective evaluations of sensory aspects of subjective experience with imaged local brain activations [2]. Such neurophenomenological program depends on the development of dynamic approaches to cerebral activity in conjunction to standardized and rigorous measurements of subjective experience obtained from first-person reports [3,4]. A particular difficulty concerning the subjective character of conscious experience is the neural substrate of sensorial qualia features such as color, sound, scent, taste, touch, pain, and the like [5]. It has been suggested that the ventral prefrontal cortex is necessary, but not sufficient, for the generation of subjective experiences [6–8] and that there may be different areas involved depending on their specific character (e.g. auditory, tactile, emotional) [9,10]. Other studies also report signal increases in frontopolar prefrontal cortex during different self- referential processing tasks [11–13] and the magnitude and time course of its activation predicts whether information is consciously perceived or slips away unnoticed [6]. Bilateral activations of temporopolar cortex were found during object encoding, tactile perception and self-related processing [14– 16]. Furthermore, the phenomenal character of perceiving some objects as different from others is associated with right tempor- opolar activation [15]. The ability to voluntarily direct, concentrate, and sustain attention can bring into focus and enhance bottom-up qualitative processes of either a somatosenory/external or proprioceptive/ internal nature [17–21]. A form of insight meditation requiring sustained awareness of subtle somatic sensations spontaneously arising from different body parts increases parieto-occipital PLOS ONE | www.plosone.org 1 August 2014 | Volume 9 | Issue 8 | e104721