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To provide full accounts of human experience and behavior, research in cognitive neuroscience must be linked to inner experience, but introspective reports of inner experience have often been found to be unreliable. The present case study aimed at providing proof of principle that introspection using one method, descriptive experience sampling (DES), can be reliably integrated with fMRI. A participant was trained in the DES method, followed by nine sessions of sampling within an MRI scanner. During moments where the DES interview revealed ongoing inner speaking, fMRI data reliably showed activation in classic speech processing areas including left inferior frontal gyrus. Further, the fMRI data validated the participant’s DES observations of the experiential distinction between inner speaking and innerly hearing her own voice. These results highlight the precision and validity of the DES method as a technique of exploring inner experience and the utility of combining such methods with fMRI.
There is a large literature in both cognitive neuroscience and behavioral psychology that seeks to characterize aspects of inner experience. A growing subset of studies has sought to use fMRI to identify neural correlates of inner experience, for example by studying thinking that is not tightly related to the current task. This has been variously called mind wandering (
Capturing the incidence and flow of such inner experience is an intriguing challenge for neuroimaging. Undirected thoughts have been mostly studied either by contrasting passive “baseline” periods with an active, stimulus-driven task (see
Recently a number of novel methods have been developed to induce and examine undirected thoughts, most of which have targeted instances of mind wandering. One approach is to train participants on a particular cognitive task that is conducive to mind wandering, deploy the task in the scanner, ask participants to report instances of mind wandering, and then correlate this with DMN activity (
These methods offer novel ways of investigating undirected thoughts. Nevertheless, they all involve a trade-off of some kind. Experiences can be sampled immediately by asking participants to make a forced-choice discrimination while in the scanner. But such techniques almost always preclude detailed descriptions of experience; experience sampling techniques are typically used simply as classifiers of two or three different “modes” of thinking (such as being “on-task” vs. “off-task”;
A technique with the potential to offer an alternative method is descriptive experience sampling (DES;
There are five experiential phenomena that DES claims occur frequently (
The DES process can produce surprising results. For example, inner speech is held by some to occur during every waking moment (
In contrast to other methods, then, DES aims to clear out these assumptions and train participants to be more careful in reporting their experiences by avoiding generalizations, focusing on a precise moment (just before the beep), and interviewing participants not just once but on multiple occasions, in an iterative manner (
Two of us (SK, a neuroscientist, and CF, a psychologist) invited DES-creator Hurlburt (hereafter called RH, whose work we knew but with whom we had no relationship) to put the DES method to the test. We recruited five participants, all unknown to RH and unrelated to us, and invited RH to perform a typical DES investigation with each. Data on all five participants is reported elsewhere as part of a wider study (Hurlburt et al., in preparation). Our aim here is to establish proof-of-principle in a single participant that idiographic investigation of inner experience, such as is provided by DES, can be successfully combined with fMRI. As such we only report here on one of those participants, “Lara,” an 18 year-old-woman. As with the other participants, RH trained Lara in the usual DES way (four sampling days in her natural environments); then we delivered random DES beeps to her in nine sessions while she was in an MRI scanner, four random beeps per 25-min session. Immediately after each session, RH conducted a typical DES interview with her about the four beeped experiences. Before the fMRI data were analyzed, RH descriptively characterized those 36 in-the-scanner moments of Lara’s experience; these 36 DES characterizations were used to form participant-specific categories on which the fMRI contrasts would be based.
In a preliminary phase at the start of the study, for possible comparison with the DES results, we also asked Lara to perform conventional neuroscience imagination tasks in the scanner: we directed her to generate specific verbal, auditory, visual, emotional, and somatosensory imagery when instructed by prompts such as “to see a pencil” or “to say ‘lamp’.” These conventional tasks could then be used to test whether the neuroimaging results derived from the DES method were plausible, localizable, and comparable to brain activity determined by conventional (non-introspective) means.
Because of the idiographic, open-beginninged nature of DES, at the outset of Lara’s DES sampling, we had no expectations about whether one or more of the 5FP might emerge as a salient characteristic of her inner experience. Nonetheless, to facilitate nomothetic comparison it is useful to consider the 5FP if they emerge. It turned out that for Lara, according to DES, sensory awareness was the most frequent of the 5FP (27 occasions or 75% of Lara’s 36 in-scanner samples); however, its varying modality (visual, bodily, auditory, etc.) made it an unlikely candidate for neural correlation. Inner seeing occurred in 8 (22%) of Lara’s 36 in-scanner samples; however, inner seeing had never occurred in Lara’s natural environment DES sampling, so it seemed likely to be an artifact of the scanner situation. Inner speaking occurred in 8 (22%) of Lara’s 36 in-scanner samples; it had also occurred in 13% of Lara’s natural environment DES sampling, so inner speaking seems a good candidate for further consideration. Of the remaining 5FP phenomena, unsymbolized thinking and feelings were too rare [one occasion (3%) each]. (Percentages do not add to 100% because multiple ratings are possible.) Thus, as a result of Lara’s idiographic experiential result, we will focus here on Lara’s inner speech-related neural processing.
The neuroimaging literature suggests that language or speech-based samples are typically associated with brain areas such as left inferior frontal gyrus (IFG), superior temporal sulcus (STS), and the superior and middle temporal gyri (
The study was conducted according to the Declaration of Helsinki, with approval of the German Psychological Society Ethics Committee.
Lara was scheduled for 19 sessions across a 2-week period, which was divided into four phases. She was right-handed and aged 18.
In Phase 1 (
In Phase 2 (
In Phase 3 (
In Phase 4 (
Images were collected on a 3T Magnetom Trio MRI scanner system (Siemens Medical Systems, Erlangen, Germany) using a 32-channel radio frequency head coil. Structural images were obtained using a three-dimensional T1-weighted magnetization-prepared gradient-echo sequence (MPRAGE) based on the ADNI protocol (
The fMRI data were analyzed using SPM8 software (Wellcome Department of Cognitive Neurology, London, UK). The first four volumes of all EPI series were excluded from the analysis to allow the magnetization to approach a dynamic equilibrium. Data processing started with slice time correction and realignment of the EPI datasets. A mean image for all EPI volumes was created, to which individual volumes were spatially realigned by means of rigid body transformations. The structural image was co-registered with the mean image of the EPI series. Then the structural image was normalized to the Montreal Neurological Institute (MNI) template, and the normalization parameters were applied to the EPI images to ensure an anatomically informed normalization. A commonly applied filter of 8 mm full-width at half maximum (FWHM) was used. Low-frequency drifts in the time domain were removed by modeling the time series for each voxel by a set of discrete cosine functions to which a cut-off of 128 s was applied. The statistical analyses were performed using the general linear model (GLM).
The imagination task was modeled as blocks with a duration of 32 s. The beeps of the DES procedure were modeled as events on the onset of the beep with a duration of 0. These vectors were convolved with a canonical hemodynamic response function (HRF) and its temporal derivatives.
For the DES procedure, we asked RH, on the basis of the DES expositional interviews he (and others) had conducted, to classify each of Lara’s 36 in-the-scanner experiences into four modalities: verbal, visual, bodily, and auditory (categories could overlap). We also asked RH to classify each of Lara’s experiences according to which (if any) of the 5FP (inner speaking, inner seeing, unsymbolized thinking, feeling, and sensory awareness) were present. RH’s classifications were checked by at least one other person who had been present at the relevant interview; disagreements were resolved by consensus. Then, regressors were built coding the categories that RH had assigned to the 36 events. For display purposes the resulting SPMs were thresholded at
In Phase 1 (
Conventional imagination task: inner saying > fixation (FWE
Area | BA | Peak coordinates (MNI) | Extent | ||
---|---|---|---|---|---|
Left rolandic operculum | 6 | -48, 2, 46 | 11.74 | 430 | 0.000 |
Left dorsolateral prefrontal cortex (DLPFC), inferior frontal gyrus (IFG) | 46, 45 | -39, 35, 34 | 9.14 | 337 | 0.000 |
Left middle temporal gyrus | 21 | -51, -49, 10 | 8.92 | 80 | 0.000 |
Left middle temporal gyrus | 21 | -66, -46, 4 | 8.06 | 77 | 0.000 |
Right visual cortex | 18 | 30, -97, 4 | 8.00 | 78 | 0.000 |
Right cerebellum (Crus 2) | 18, -82, -32 | 7.97 | 272 | 0.000 | |
Left visual cortex | 18 | -33, -97, -5 | 7.62 | 23 | 0.000 |
Left angular gyrus | 39 | -45, -61, 49 | 7.02 | 107 | 0.000 |
Right temporal pole | 38 | 51, 20, -29 | 6.60 | 103 | 0.000 |
Left temporal pole | 38 | -33, 20, -26 | 6.60 | 106 | 0.000 |
Ventromedial prefrontal cortex | 11 | -3, 53, -17 | 6.04 | 26 | 0.000 |
Left IFG | 45 | -51, 20, 1 | 5.98 | 25 | 0.000 |
There was no fMRI data collected during Phase 2. In Phase 3 we ask first whether the DES interviews conducted by RH are capable of classifying Lara’s verbal experience in ways that correspond to her neurophysiological activation.
Descriptive experience sampling modalities: verbal modality > all other categories (
Area | BA | Peak coordinates (MNI) | Extent | ||
---|---|---|---|---|---|
Right postcentral gyrus | 3 | 48, -22, 43 | 5.05 | 102 | 0.000 |
Left IFG | 45 | -51, 29, 10 | 4.24 | 31 | 0.000 |
Anterior cingulate gyrus | 32 | 0, 20, 43 | 4.02 | 34 | 0.000 |
Next in Phase 3, we examine the 5FP category of inner speaking. Samples that included inner speaking were spread throughout the scanning sessions: three samples occurred during the third scanning session, one each during the fourth, seventh, and eighth scans, and two during the ninth scan. We modeled brain activity across all 36 samples as a function of whether RH had said inner speaking was or was not present. We did the same kind of univariate modeling across all 36 samples for each of the remaining four 5FP characteristics (that is, for inner seeing, for unsymbolized thinking, for feelings, and for sensory awareness). Then across the eight samples in which RH had said inner speaking was present, we compared the average of results of the inner speaking model to the average of the results of the four remaining models; this analysis indicated the presence of activity in left IFG, the core of the inner speech network (
Descriptive experience sampling 5FP: inner speaking > all other categories (
Area | BA | Peak coordinates (MNI) | Extent | ||
---|---|---|---|---|---|
Left IFG | 45 | -36, 32, 19 | 4.96 | 88 | 0.000 |
Left DLPFC | 9 | -12, 41, 43 | 4.26 | 58 | 0.000 |
Because DES is primarily an idiographic technique, it is held to be capable of describing characteristics that apply to one individual, regardless of whether those characteristics are important for many or any other individuals. Therefore we asked RH to identify characteristics that might emerge from Lara’s participation in the DES procedure (during either or both the natural environment and the in-the-scanner phases) that are not standard modality features (verbal, visual, bodily, and auditory) and that are not identified as 5FP, regardless of whether the feature was a characteristic of any other DES participant. One such feature that RH noted was that when Lara experienced inner words, they ranged on a continuum from innerly spoken to innerly heard (
Descriptive experience sampling idiographic: inner speaking > Inner hearing (
Area | BA | Peak coordinates (MNI) | Extent | ||
---|---|---|---|---|---|
Left IFG | 45 | -51, 41, -5 | 3.87 | 23 | 0.000 |
To summarize, whether prompted using a conventional imagery-based fMRI paradigm or classified via use of the DES, Lara’s experiences of inner speaking were, as expected, reliably associated with activation in left IFG. This validates the suggestion that it is indeed possible for the DES procedure to apprehend features of inner experience and to do so as they naturally occur—the present study, for example, did not set out to investigate inner speaking; it set out to investigate naturally occurring characteristics of Lara’s inner experience
The validation of high fidelity apprehensions of inner experience demonstrated in the present study should not be taken as a validation of all introspective or subjective reports—DES is, by
The combination of phenomenology and neurophysiology might be understood as a validation of DES: claims about private experience are always questionable, and the fact that the DES claims correlate with known neurophysiological results lends non-trivial support to the adequacy of the DES claims. However, the validation could be understood to operate the other way around: that the DES descriptions lend support to fMRI techniques as a way of investigating short-duration phenomenological characteristics. Either way, such a merger might answer important questions that are impossible even to pose without experiential data aimed at particular moments of consciousness. Here are two examples. First, Lara’s inner speaking results show that (at least for Lara) there is a phenomenological distinction between innerly speaking one’s voice and innerly hearing one’s voice being spoken. To our knowledge, such a distinction is typically not attended to in contemporary models of inner speech (
Also of interest was the relatively wider spread of activation associated with imagined inner speech (
Given that this is a single case, we do not know whether distinctions such as between inner speaking and inner hearing and between prompted and unprompted inner speaking reflect idiosyncratic characteristics of Lara (and/or of RH) or are characteristic of other individuals who would regularly report inner speaking as part of their everyday experience. The present study cannot answer such questions, but it does provide a method whereby such questions might be answered.
Furthermore, this study does not by itself establish a principle about introspections in general, because it investigated only one method (DES) and one investigator (RH). For example, this study should
However, this study does suggest a new set of opportunities for cognitive neuroscience investigations. Most fMRI studies ask the participant in the scanner to perform a task that indirectly invokes a particular set of brain functions in the scanner. Whether receptive (e.g., merely viewing a flashing display) or active (e.g., memorizing syllables), the aim of those tasks is indirect in the sense that the task and stimuli are presumed to elicit the desired brain functions. That is, participants do not observe or report any aspect of their brain or mental function; they simply engage in the task that presumably indirectly evokes the brain function.
As noted in the Introduction, some fMRI studies ask participants in the scanner directly to rate their cognition or mental activity on some predefined measure (e.g.,
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We thank Lara. We acknowledge the support of the Max Planck Institute and Wellcome Trust grant WT098455MA. The genesis of this study was a workshop grant from the Volkswagen Foundation to Felicity Callard, Des Fitzgerald, Simone Kühn, and Ulla Schmid.