diff --git a/bids/layout/models.py b/bids/layout/models.py
index 766edd14..cd39426f 100644
--- a/bids/layout/models.py
+++ b/bids/layout/models.py
@@ -309,7 +309,7 @@ class BIDSDataFile(BIDSFile):
     }
 
     def get_df(self, include_timing=True, adjust_onset=False,
-               enforce_dtypes=True):
+               enforce_dtypes=True, **pd_args):
         """Return the contents of a tsv file as a pandas DataFrame.
 
         Parameters
@@ -326,6 +326,8 @@ class BIDSDataFile(BIDSFile):
             If True, enforces the data types defined in
             the BIDS spec on core columns (e.g., subject_id and session_id
             must be represented as strings).
+        pd_args : dict
+            Optional keyword arguments to pass onto pd.read_csv().
 
         Returns
         -------
@@ -347,8 +349,10 @@ class BIDSDataFile(BIDSFile):
         # TODO: memoize this for efficiency. (Note: caching is insufficient,
         # because the dtype enforcement will break if we ignore the value of
         # enforce_dtypes).
+        suffix = self.entities['suffix']
+        header = None if suffix in {'physio', 'stim'} else 'infer'
         self.data = pd.read_csv(self.path, sep='\t', na_values='n/a',
-                                dtype=dtype)
+                                dtype=dtype, header=header, **pd_args)
 
         data = self.data.copy()
 

First line omitted when using get_df() method of BIDSDataFile object
Hi,

The method `get_df() `of the BIDSDataFile object omits the first line of the data file. This issue arises when calling the function `read_csv()` of Pandas, as header is set to 0 if no names are passed:

```
self.data = pd.read_csv(self.path, sep='\t', na_values='n/a',
                                dtype=dtype)
```

This behaviour can be problematic if one is working with the physiological recording data, since they  don't have a header line and therefore the first observation would be always lost. 

This could be solved by modifying the piece of code above as follows:

```
if self.entities['suffix'] == 'physio' or 'stim':
    self.data = pd.read_csv(self.path, sep='\t', na_values='n/a', 
                            header=None, dtype=dtype)
else:
    self.data = pd.read_csv(self.path, sep='\t', na_values='n/a',
                            dtype=dtype)
```

Does this modification make sense?

diff --git a/bids/layout/tests/test_models.py b/bids/layout/tests/test_models.py
index b6a15e73..770999fd 100644
--- a/bids/layout/tests/test_models.py
+++ b/bids/layout/tests/test_models.py
@@ -176,7 +176,7 @@ def test_bidsfile_get_df_from_tsv_gz(layout_synthetic):
     df1 = bf.get_df()
     df2 = bf.get_df(include_timing=True)
     assert df1.equals(df2)
-    assert df1.shape == (1599, 3)
+    assert df1.shape == (1600, 3)
     assert set(df1.columns) == {'onset', 'respiratory', 'cardiac'}
     assert df1.iloc[0, 0] == 0.
     assert df1.iloc[1, 0] - df1.iloc[0, 0] == 0.1
@@ -190,6 +190,7 @@ def test_bidsfile_get_df_from_tsv_gz(layout_synthetic):
 def test_bidsdatafile_enforces_dtype(layout_synthetic):
     bf = layout_synthetic.get(suffix='participants', extension='tsv')[0]
     df = bf.get_df(enforce_dtypes=False)
+    assert df.shape[0] == 5
     assert df.loc[:, 'subject_id'].dtype == int
     assert df.loc[:, 'subject_id'][0] == 1
     df = bf.get_df(enforce_dtypes=True)

pip install -e .[dev]
parse_log_pytest
requirements.txt
numpy>=1.16.0 pandas>=1.0.0 nibabel patsy BIDS-Validator num2words pytest pytest-cov pytest-xdist pytest-mock pytest-asyncio
3.7
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
alabaster==0.7.13
Babel==2.14.0
bids-validator==1.14.0
certifi @ file:///croot/certifi_1671487769961/work/certifi
charset-normalizer==3.4.1
coverage==7.2.7
docopt==0.6.2
docutils==0.17.1
exceptiongroup==1.2.2
execnet==2.0.2
greenlet==3.1.1
idna==3.10
imagesize==1.4.1
importlib-metadata==6.7.0
iniconfig==2.0.0
Jinja2==3.0.3
m2r==0.3.1
MarkupSafe==2.1.5
mistune==0.8.4
mock==5.2.0
nibabel==4.0.2
num2words==0.5.14
numpy==1.21.6
numpydoc==1.2.1
packaging==24.0
pandas==1.3.5
patsy==1.0.1
pluggy==1.2.0
-e git+https://github.com/bids-standard/pybids.git@5fab1dee770babffa7aef668b24cb59a90ba37ef#egg=pybids
Pygments==2.17.2
pytest==7.4.4
pytest-asyncio==0.21.2
pytest-cov==4.1.0
pytest-mock==3.11.1
pytest-xdist==3.5.0
python-dateutil==2.9.0.post0
pytz==2025.2
requests==2.31.0
scipy==1.7.3
six==1.17.0
snowballstemmer==2.2.0
Sphinx==2.4.5
sphinx-rtd-theme==1.3.0
sphinxcontrib-applehelp==1.0.2
sphinxcontrib-devhelp==1.0.2
sphinxcontrib-htmlhelp==2.0.0
sphinxcontrib-jquery==4.1
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.3
sphinxcontrib-serializinghtml==1.1.5
SQLAlchemy==2.0.40
tomli==2.0.1
typing_extensions==4.7.1
urllib3==2.0.7
zipp==3.15.0

name: pybids
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2022.12.7=py37h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.4.4=h6a678d5_1
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=22.3.1=py37h06a4308_0
  - python=3.7.16=h7a1cb2a_0
  - readline=8.2=h5eee18b_0
  - setuptools=65.6.3=py37h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.38.4=py37h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - alabaster==0.7.13
      - babel==2.14.0
      - bids-validator==1.14.0
      - charset-normalizer==3.4.1
      - coverage==7.2.7
      - docopt==0.6.2
      - docutils==0.17.1
      - exceptiongroup==1.2.2
      - execnet==2.0.2
      - greenlet==3.1.1
      - idna==3.10
      - imagesize==1.4.1
      - importlib-metadata==6.7.0
      - iniconfig==2.0.0
      - jinja2==3.0.3
      - m2r==0.3.1
      - markupsafe==2.1.5
      - mistune==0.8.4
      - mock==5.2.0
      - nibabel==4.0.2
      - num2words==0.5.14
      - numpy==1.21.6
      - numpydoc==1.2.1
      - packaging==24.0
      - pandas==1.3.5
      - patsy==1.0.1
      - pluggy==1.2.0
      - pybids==0.10.2+69.g5fab1dee
      - pygments==2.17.2
      - pytest==7.4.4
      - pytest-asyncio==0.21.2
      - pytest-cov==4.1.0
      - pytest-mock==3.11.1
      - pytest-xdist==3.5.0
      - python-dateutil==2.9.0.post0
      - pytz==2025.2
      - requests==2.31.0
      - scipy==1.7.3
      - six==1.17.0
      - snowballstemmer==2.2.0
      - sphinx==2.4.5
      - sphinx-rtd-theme==1.3.0
      - sphinxcontrib-applehelp==1.0.2
      - sphinxcontrib-devhelp==1.0.2
      - sphinxcontrib-htmlhelp==2.0.0
      - sphinxcontrib-jquery==4.1
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==1.0.3
      - sphinxcontrib-serializinghtml==1.1.5
      - sqlalchemy==2.0.40
      - tomli==2.0.1
      - typing-extensions==4.7.1
      - urllib3==2.0.7
      - zipp==3.15.0
prefix: /opt/conda/envs/pybids

bids/layout/tests/test_models.py::test_bidsfile_get_df_from_tsv_gz[None] bids/layout/tests/test_models.py::test_bidsfile_get_df_from_tsv_gz[bidsdb-synth0] bids/layout/tests/test_models.py::test_bidsfile_get_df_from_tsv_gz[bidsdb-synth1]
bids/layout/tests/test_models.py::test_load_existing_config
bids/layout/tests/test_models.py::test_entity_initialization bids/layout/tests/test_models.py::test_entity_init_all_args bids/layout/tests/test_models.py::test_entity_init_with_bad_dtype bids/layout/tests/test_models.py::test_entity_matches bids/layout/tests/test_models.py::test_entity_deepcopy bids/layout/tests/test_models.py::test_file_associations bids/layout/tests/test_models.py::test_tag_init bids/layout/tests/test_models.py::test_tag_dtype bids/layout/tests/test_models.py::test_entity_add_file bids/layout/tests/test_models.py::test_config_init_with_args bids/layout/tests/test_models.py::test_bidsdatafile_enforces_dtype[None] bids/layout/tests/test_models.py::test_bidsjsonfile[None] bids/layout/tests/test_models.py::test_bidsfile_get_metadata[None] bids/layout/tests/test_models.py::test_bidsfile_get_entities[None] bids/layout/tests/test_models.py::test_bidsdatafile_enforces_dtype[bidsdb-synth0] bids/layout/tests/test_models.py::test_bidsjsonfile[bidsdb-synth0] bids/layout/tests/test_models.py::test_bidsfile_get_metadata[bidsdb-synth0] bids/layout/tests/test_models.py::test_bidsfile_get_entities[bidsdb-synth0] bids/layout/tests/test_models.py::test_bidsdatafile_enforces_dtype[bidsdb-synth1] bids/layout/tests/test_models.py::test_bidsjsonfile[bidsdb-synth1] bids/layout/tests/test_models.py::test_bidsfile_get_metadata[bidsdb-synth1] bids/layout/tests/test_models.py::test_bidsfile_get_entities[bidsdb-synth1] bids/layout/tests/test_models.py::test_bidsimagefile_get_image bids/layout/tests/test_models.py::test_bidsfile_fspath
bids/layout/models.py
bids/layout/models.py