[FIX] restructure and clarify *_physio/*_stim section

src/04-modality-specific-files/06-physiological-and-other-continuous-recordings.md

@@ -13,11 +13,20 @@ sub-<label>/[ses-<label>/]
 
 Optional: Yes
 
-Where `<matches>` corresponds to task file name without the `_bold.nii[.gz]`
-suffix. For example: `sub-control01_task-nback_run-1`. If the same continuous
-recording has been used for all subjects (for example in the case where they
-all watched the same movie) one file can be used and placed in the root
-directory. For example:`task-movie_stim.tsv.gz`
+In the template file names, the `<matches>` part corresponds to task file name
+without the suffix.
+For example for the file `sub-control01_task-nback_run-1_bold.nii.gz`,
+`<matches>` would correspond to `sub-control01_task-nback_run-1`.
+
+The `recording-<label>` entity can be used to distinguish between several
+recording files.
+For example `sub-01_task-bart_recording-eyetracking_physio.tsv.gz` to contain
+the eyetracking data in a certain sampling frequency, and
+`sub-01_task-bart_recording-breathing_physio.tsv.gz` to contain respiratory
+measurements in a different sampling frequency.
+
+Physiological recordings (including eyetracking) SHOULD use the `_physio`
+suffix, and signals related to the stimulus SHOULD use `_stim` suffix.
 
 Physiological recordings such as cardiac and respiratory signals and other
 continuous measures (such as parameters of a film or audio stimuli) can be
@@ -33,45 +42,14 @@ line) and a JSON for storing the following metadata fields:
 Additional metadata may be included as in
 [any TSV file](../02-common-principles.md#tabular-files) to specify, for
 example, the units of the recorded time series.
-Please note that in contrast to other TSV files this one does not include a
-header line. Instead the name of columns are specified in the JSON file.
-This is to improve compatibility with existing software (FSL PNM) as
-well as make support for other file formats possible in the future.
-Recordings with different sampling frequencies and/or starting times should be
-stored in separate files.
-The following naming conventions should be used for column names:
-
-| Column name | Definition                                           |
-| ----------------- | ------------------------------------------------------- |
-| cardiac     | continuous pulse measurement                         |
-| respiratory | continuous breathing measurement                     |
-| trigger     | continuous measurement of the scanner trigger signal |
-
-Any combination of those three can be included as well as any other stimuli
-related continuous variables (such as low level image properties in a video
-watching paradigm).
+Please note that in contrast to other TSV files in BIDS, the TSV files specified
+for phsyiological and other continuous recordings *do not* include a header
+line.
+Instead the name of columns are specified in the JSON file.
+This is to improve compatibility with existing software (e.g., FSL, PNM) as well
+as to make support for other file formats possible in the future.
 
-Physiological recordings (including eye tracking) should use the `_physio`
-suffix, and signals related to the stimulus should use `_stim` suffix. For
-motion parameters acquired from scanner side motion correction please use
-`_physio` suffix.
-
-More than one continuous recording file can be included (with different sampling
-frequencies). In such case use different labels. For example:
-`_recording-contrast`, `_recording-saturation`. The full file name could then
-look like this: `sub-control01_task-nback_run-2_recording-movie_stim.tsv.gz`
-
-For multi-echo data, physio.tsv file is applicable to all echos of particular
-run. For eg:
-
-```Text
-sub-01_task-cuedSGT_run-1_physio.tsv.gz
-sub-01_task-cuedSGT_run-1_echo-1_bold.nii.gz
-sub-01_task-cuedSGT_run-1_echo-2_bold.nii.gz
-sub-01_task-cuedSGT_run-1_echo-3_bold.nii.gz
-```
-
-Example:
+Example for `*.tsv.gz`:
 
 ```Text
 sub-control01/
@@ -82,11 +60,13 @@ sub-control01/
 (after decompression)
 
 ```Text
-34  110 0
-44  112 0
-23  100 1
+34 110 0
+44 112 0
+23 100 1
 ```
 
+Example for `*.json`:
+
 ```Text
 sub-control01/
     func/
@@ -97,9 +77,45 @@ sub-control01/
 {
    "SamplingFrequency": 100.0,
    "StartTime": -22.345,
-    "Columns": ["cardiac", "respiratory", "trigger"],
+   "Columns": ["cardiac", "respiratory", "trigger"],
    "cardiac": {
        "Units": "mV"
    }
 }
 ```
+
+## Additional rules
+
+To store pulse or breathing measurements, or the scanner trigger signal, the
+following naming conventions SHOULD be used for the column names:
+
+| Column name | Definition                                           |
+| ----------------- | ------------------------------------------------------- |
+| cardiac     | continuous pulse measurement                         |
+| respiratory | continuous breathing measurement                     |
+| trigger     | continuous measurement of the scanner trigger signal |
+
+For any other data to be specified in columns, the column names can be chosen
+as deemed appropriate by the researcher.
+
+Recordings with different sampling frequencies and/or starting times should be
+stored in separate files.
+
+If the same continuous recording has been used for all subjects (for example in
+the case where they all watched the same movie), one file MAY be used and
+placed in the root directory.
+For example:`task-movie_stim.tsv.gz`
+
+For motion parameters acquired from scanner side motion correction, the
+`_physio` suffix SHOULD be used.
+
+For multi-echo data, a given `physio.tsv` file is applicable to all echos of
+a particular run.
+For example:
+
+```Text
+sub-01_task-cuedSGT_run-1_physio.tsv.gz
+sub-01_task-cuedSGT_run-1_echo-1_bold.nii.gz
+sub-01_task-cuedSGT_run-1_echo-2_bold.nii.gz
+sub-01_task-cuedSGT_run-1_echo-3_bold.nii.gz
+```