def get_single_field(fields):
    """Finds neurons with and indices of single fields.

    Parameters
    ----------
    fields : dict
        Where the key is the neuron number (int), value is a list of arrays (int).
        Each inner array contains the indices for a given place field.
        Eg. Neurons 7, 3, 11 that have 2, 1, and 3 place fields respectively would be:
        {7: [[field], [field]], 3: [[field]], 11: [[field], [field], [field]]}

    Returns
    -------
    fields : dict
        Where the key is the neuron number (int), value is a list of arrays (int).
        Each inner array contains the indices for a given place field.
        Eg. For the above input, only neuron 3 would be output in this dict:
        {3: [[field]]}

    """
    fields_single = dict()
    for neuron in fields.keys():
        if len(fields[neuron]) == 1:
            fields_single[neuron] = fields[neuron]
    return fields_single
