FB2026_03 , released September 17, 2026
CV Term Report
Help Close All Open All
General Information
Term horizontal system neuron ID (Ontology) FBbt:00003917 (Fly Anatomy)
Definition Giant neuron with wide-field dendritic arborization in lobula plate layer 1 (Shinomiya et al., 2022). This arborization is flattened in the anterior-posterior axis (Scott et al., 2002). Most of its input is from T4a and T5a neurons (Shinomiya et al., 2022). Its axon extends medially and ventrally to innervate the adult protocerebrum (Scott et al., 2002). It is involved in the optomotor response (Heisenberg et al., 1978; Schnell et al., 2010) and responds to horizontal motion with graded membrane potential changes in a directional-selective way (Schnell et al., 2010).[ FlyBase:FBrf0032046 FlyBase:FBrf0049410 FlyBase:FBrf0155898 FlyBase:FBrf0179400 FlyBase:FBrf0200428 FlyBase:FBrf0207482 FlyBase:FBrf0210299 FlyBase:FBrf0254308 ]
Also Known As"giant horizontal cell" ; "HS" ; "HS cell"
CommentDue to their morphology and functional similarity, these cells are judged to be homologous to the three horizontal system cells in larger flies (Heisenberg et al., 1978; Rajashekhar and Shamprasad, 2004; Scott et al., 2002). The presynaptic terminals in the protocerebral region were identified by the presence of a subunit of the GABA receptor (Rdl) in horizontal system cells labelled with the P\{GAL4\}3A driver (FBti0131277). The postsynaptic terminals in the protocerebral region were labelled with P\{UAS-n-syb.mRed\} (FBtp0055749] driven by the P\{GAL4\}3A driver [FBti0131277) (Raghu et al., 2007).
Links to External Ontologies
VFB:FBbt_00003917
Annotations
Records annotated with this term OR any of its CHILD TERMS

Choose a record type to view annotations for this term and its child terms. Direct annotations and full annotation statements below also provide HitList buttons.

    • Results list data from multiple species. Choose a record type above to open its HitList.
Direct annotations: records annotated with this exact term (child terms are NOT included)
Data ClassFieldDirect annotations
Alleles (FBal)PHENOTYPE_MANIFEST_IN
Insertions (FBti)EXPRESSION_STAGE_TISSUE_POSITION
show Full annotation statements including this term (annotations to child terms are NOT included), and relevant FlyBase records
 Full annotation statements 
Relevant FlyBase reports
 Alleles Split System Combinations Genes Insertions Constructs
 horizontal system neuron (all annotations which use CV term, excluding "NOT" statements)
Spanning Tree (Parents/Children)
Only view relationship:
Vocabulary search 
adult brain
 |__adult visual projection neuron__
lobula plate tangential neuron      |
 |__lobula plate giant neuron_______|
visual projection neuron            |
 |__adult visual projection neuron__|
adult interneuron                   |
 |__adult visual projection neuron__|
                                    horizontal system neuron  24 rec.
                                     |__dorsal giant horizontal cell HSN 5 rec.
                                     |__equatorial giant horizontal cell HSE 5 rec.
                                     |__horizontal twin cell HST
                                     |__ventral giant horizontal cell HSS 2 rec.
Spanning Tree View Settings
Parents/Children
View Depth
Show hierarchy levels: for parents, for children
hide Relationships
Is a lobula plate giant neuron
adult visual projection neuron
Part of
hide Synonyms & Secondary IDs
Synonyms
Secondary IDs
hide External Crossreferences & Linkouts
FlyBrain_NDB:10043
VFB:FBbt_00003917