def select_data(all_tetrode_data, index):
    """
    Select tetrode data by trial indices.

    :param all_tetrode_data: (list of 4d numpy arrays) each of format [trial, 1, neuron + tetrode, time]
    :param index: (1d numpy array) trial indices
    :return: (list of 4d numpy arrays) selected subset of tetrode data
    """
    current_data = []
    for x in all_tetrode_data:
        current_data.append(x[index, :, :, :])
    return current_data