allow ieeg channel names to contain more than letters+numbers

src/04-modality-specific-files/04-intracranial-electroencephalography.md

@@ -231,7 +231,7 @@ MUST be present:
 
 | Column name  | Definition                                                                                                                                                                                                                                                                                                                               |
 | :----------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| name         | REQUIRED. Label of the channel, only contains letters and numbers. The label must correspond to \_electrodes.tsv name and all ieeg type channels are required to have a position. The reference channel name MUST be provided in the reference column.                                                                                   |
+| name         | REQUIRED. Label of the channel. The label must correspond to \_electrodes.tsv name and all ieeg type channels are required to have a position. The reference channel name MAY be provided in the reference column.                                                                                                                       |
 | type         | REQUIRED. Type of channel, see below for adequate keywords in this field.                                                                                                                                                                                                                                                                |
 | units        | REQUIRED. Physical unit of the value represented in this channel, e.g., V for Volt, specified according to the [SI unit symbol](https://en.wikipedia.org/wiki/International_System_of_Units#Base_units) and possibly prefix symbol (e.g., mV, μV). For guidelines for Units and Prefixes see [Appendix V](../99-appendices/05-units.md). |
 | low_cutoff   | REQUIRED. Frequencies used for the low pass filter applied to the channel in Hz. If no low pass filter was applied, use `n/a`. Note that anti-alias is a low pass filter, specify its frequencies here if applicable.                                                                                                                    |