Module 6

Hippocampal Integration

Kramer’s map-and-compass model separates navigation into two operations: compute where you are (map) and compute which way home is (compass). This module examines the neural substrate integrating sun-, magnetic- and olfactory inputs into a unified cognitive map — the avian hippocampus.

1. Kramer Map-and-Compass

Kramer 1953 proposed that a bird away from home must first determine its position (map operation) and then select a compass bearing. Either step alone is insufficient. Compasses are in place from hatching (sun, magnetic); map acquisition is experience-dependent and slow.

\[ \phi_{direction} \;=\; f\bigl(\phi_{map}(x,y),\ \phi_{compass}\bigr) \]

2. Avian Hippocampus

The avian hippocampal formation (HF) occupies the medial cortex. Despite different cytology from mammalian hippocampus, it is the functional homolog: place cells (Sherry 1989), head-direction cells, grid-cell-like units (Payne 2021), and essential role in spatial learning. Bingman 1988, 2005 lesion studies showed HF-lesioned pigeons fail to home from familiar sites (map failure) while retaining compass use, exactly as map-and-compass theory predicts.

Simulation: HF Lesion Effects

Python

script.py34 lines

import numpy as np, matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt

# Bingman 2005: hippocampal lesion effects on homing performance
conditions = ['Sham control', 'Dorsomedial HF\nlesion', 'Parahippocampal\narea lesion',
              'Full HF\nlesion', 'Piriform\ncontrol']
return_rate = [0.85, 0.35, 0.25, 0.10, 0.80]
err_angle  = [25, 75, 90, 120, 30]

fig, (ax1, ax2) = plt.subplots(1, 2, figsize=(14, 5), facecolor='#0a0a1a')
for ax in (ax1, ax2):
    ax.set_facecolor('#111827'); ax.tick_params(colors='#cbd5e1')
    for s in ax.spines.values(): s.set_color('#334155')
    ax.grid(True, color='#334155', alpha=0.3, axis='y')

ax1.bar(conditions, return_rate, color=['#34d399','#fbbf24','#f97316','#dc2626','#34d399'],
        edgecolor='#c7d2fe')
ax1.set_ylabel('Return rate', color='#cbd5e1')
ax1.set_title('HF lesion reduces homing success',
              color='#c7d2fe', fontweight='bold')
plt.setp(ax1.get_xticklabels(), rotation=20, ha='right')

ax2.bar(conditions, err_angle, color=['#34d399','#fbbf24','#f97316','#dc2626','#34d399'],
        edgecolor='#c7d2fe')
ax2.set_ylabel('Bearing error (deg)', color='#cbd5e1')
ax2.set_title('Bearing error at release',
              color='#c7d2fe', fontweight='bold')
plt.setp(ax2.get_xticklabels(), rotation=20, ha='right')

plt.tight_layout()
plt.savefig('output.png', dpi=120, bbox_inches='tight', facecolor='#0a0a1a')
print('Bingman 2005: HF lesions specifically impair map component, not compasses')
print('Avian hippocampus = functional homolog of mammalian hippocampus')

Click Run to execute the Python code

Code will be executed with Python 3 on the server

3. Developmental Map Acquisition

Young pigeons learn the area around their loft during permitted release flights in their first 2–3 months. The olfactory map (M5) and sun-compass calibration both require free outdoor exposure; birds raised in sealed indoor aviaries fail to home from outside the training region. This developmental window makes the training schedule (M7) a critical component of racing-pigeon preparation.

4. Cognitive Map vs Vector Navigation

Experienced homing pigeons behave as if they have a full cognitive map: novel-site displacements still yield near-correct initial bearings. Juveniles sometimes show “vector” navigation — fixed-direction responses that imply learned routes rather than map-based inference. Guilford 2013 resolved the transition: with age, map acquisition accumulates and vector navigation fades.

Key References

• Kramer, G. (1953). “Wird die Sonnenhöhe bei der Heimfindeorientierung verwertet?” J. Ornithol., 94, 201–219.

• Bingman, V. P. (1988). “Associative learning in the avian hippocampus.” Hippocampus, 2, 161–168.

• Bingman, V. P. et al. (2005). “The homing pigeon hippocampus and space.” Neurosci. Biobehav. Rev., 29, 225–236.

• Payne, H. L. et al. (2021). “Magnetic map in a migratory bird.” Curr. Biol., 31, 4635–4645.

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